2020-2021 ICS4U: Dolgin Development Platform (DDP with DDBv6)

 

What is truly unique about our ACES program is that much of the curriculum we explore is based on tools developed within RSGC by those students that have left their talents as gifts for you to benefit from. To begin to appreciate the significance of this, you are encouraged to read the history of this particular platform and the history of our program and philosophy, in general.


With each iteration of ICS4U new insights and opportunities present themselves that compel us to dig deeper. The DDBv6 is your starting point and it is your teacher's hope that, through our combined efforts and achievements, next year's ICS4U group will be looking at Version 8 (Version 7 is in development).


2020-2021 DDP Task Sequence

1. DDBv6: Assembly

Your first (pleasant) task is to prepare the hardware and software environments for the Dolgin Development Platform (DDP). On the hardware side assemble your Dolgin Development Board Version 6 (DDBv6) using the parts supplied to you. See the full Parts Table below, right. Joseph V. is deserving of special mention for supplying the 3D printed cases for the DDBv? based on Josh's design.

In our first class of Session 5.1 (January 18) we'll go over specific soldering tips and reminders for the DDBv6. Be sure to listen carefully as replacement parts are obviously difficult to address under current conditions.

On the software side, within the Arduino IDE, under Tools > Board > Boards Manager, be sure to have installed the latest ATtinyCore library by Spence Konde. You may wish to create a DDP folder within your Sketch folder area to hold this device's future software investigations.

 

PARTS TABLE
# DESCRIPTION SUPPLIED.
1 AVR ATtiny84 MCU (Microchip) S
1 IC Socket 14 Pin (CNC Tech) S
1 USB MINI B Connector (Molex) S
1 3 POS RA (kinked) Conn. Hdr (Molex) S
2 1×8 Female Header (Sullins) S
1 10 μF Electrolytic Capacitor (short) S
1 1 μF Electrolytic Capacitor (short) S
1 2.1 mm Power Jack (Schurter) S
1 2×3 Shrouded ISP Header (Wurth) S
1 Dolgin Development Platform Board V6 PCB S
1 Dolgin Development Platform Case with Insets S
4 5mm M3 Nylon Screws (McMaster-Carr) S
1 LM7805 Voltage Regulator X
2 Power (Red) and GND (Black) hookup wire X

2. DDBv6: In-System Programming

With your DDBv6 physically assembled, we are now ready to begin exploiting its capabilities. Whereas the Arduino platform has onboard USB to Serial support, our leaner DDBv6 relies on ISP programming. For this, you'll use your handy Sparkfun AVR Pocket Programmer, inserting the ISP cable into the undermounted 2×3 Shrouded ISP Header (Wurth) connector. Whereas this is a familiar and efficient means to reprogram our AVR MCUs, it does come with a significant downside as the SCK, MISO, and MOSI (PORTA4:6) pins are required to perform the reflashing. Should DDBv7 be entertained by one of you, developing a USB-to Serial programing solution, requiring only TX and RX (PORTB0:1), combined with some SMD components, would be a significant improvement.

Another design feature of the DDBv6 is that once your project is functioning, you can remove the ISP connection, detach the programmer section (pictured to the right) and simply insert its power cable into the USB MINI B Connector (Molex) connector on top to power your prototype. Very convenient (it's likely clear to you by now that the DDBv6's access point design decisions that you've encountered already were purposely intended to maintain low headroom on the top of the platform. Hence, you'll have unobstructed access to the ATtiny84's header pins).

A third power solution is the use of a 9V AC/DC Adapter with a 2.1 mm barrel jack. Again, undermounted through the 2.1 mm Power Jack (Schurter), this strategy offers the best solution for maximum power as it is not restricted to the ~400 mA current limitations associated with your computers' USB ports.


3. DDBv6: The OnBoard LED

Following the lead of Arduino boards, the DDBv6 was designed with an onboard LED tied to digital pin 8 (PORTB.2). For your first series of DDBv6 sketches you are asked to put this LED through its register-level coding paces.

Task.

  1. Click on the image below and familiarize yourself with as much of the ATtiny84's pin arrangement and functionality as possible.

  2. The MCU version of the traditional "Hello, World!" sketch is the blink sketch. Create a register-level Blink sketch that duplicates the UNO's Blink sketch on the onboard LED. You'll encounter unexpected timing results due to the MCU's default 1 MHz clock speed. a one-time burning of the bootloader restores the ATtiny84's clock speed to 8 MHz and the blinking should occur as expected.
  3. Modify your Blink sketch to confirm you can blink an LED on any of the other digital pins. You might wish to develop alternate flashing of the 3 or 5 mm bicolor LEDs.

4. DDBv6: The DDBv6XX.h Library

In programming for the ATmega328P (either the UNO or Nano) you became familiar with predefined constants such as, LED_BUILTIN. Tucked deep inside your Arduino IDE's installation is a file, called variant.h, that contain this statement (and numerous others),

#define LED_BUILTIN 13

Libraries are an integral part of the development cycle as they reduce development time and ensure greater code accuracy. It would be both instructive and efficient for you to begin to assemble reusable software assets inside your own library of support resources for the DDBv6. Since this is would be a separate file from your specific project applications, you'll need to remember to attach at least two code files when submitting for assessment. Furthermore, since I would have to distinguish between each of your libraries, I would ask that you name your library, DDBv6XX.h where XX are your initials.

Task.

  1. Create a new project sketch entitled DDBv6LibDev.
  2. Invoke the New Tab feature (under the Serial Monitor icon in the top right corner of the IDE) and create the file, DDBv6XX.h where XX are your initials.
  3. Add the definition, #define LED_BUILTIN 8 to your library.
  4. Within your driver sketch, add the statement #include "DDBv6XX.h" and add statements to capitalize on the library's only asset, to light the DDBv6's onboard LED.
  5. Add a Lookup Table (LuT) of base type uint8_t and size 16 to your DDBv6XX.h defining the 7-segment maps for each of the 16 hexadecimal digits. This LuT is to be used in conjunction with your upcoming Pin Change interrupt project.
  6. Add the function void LEDOn (uint8_t anodePin, uint8_t cathodePin) that turns on an LED, biased as per its parameters. Test this function for a bicolor LED spanning any pair of digital pins.
  7. Add further definitions and code to your library that you feel would save you development time in the future.
  8. When you are (temporarily) satisfied with the performance of your local library (DDBv6XX.h), create the folder DDBv6XX in the /libraries folder of your default Sketch folder. Drop in your DDBv6XX.h library.
  9. Global access to your library is ensured through the use of the #include <DDBv6XX.h> statement.
  10. Syntax highlighting can be achieved through the use of a keywords.txt file. Here's a lead in that direction: https://spencer.bliven.us/2012/01/18/arduino-ide-keywords/

5. DDBv6: Reset Sources

You are familiar with the effect of pressing the Reset button on the UNO or Nano, however further optimization is accessible through a deeper understanding of subtleties the various Reset sources of AVR MCUs. These sources can be detected and subsequently impact how your code chooses to restart.

Chapter 9 of the ATtiny84 datasheet introduces the concept of System Control and, in particular, the Reset Function. The MCU offers four hardware Reset triggers that include: Power On, External, BrownOut, and Watchdog. At the end of this chapter, there is a description of the Registers that can be inspected and manipulated. For our purposes, we'll limit ourselves to a simple distinction between the Power On and External Reset triggers. Page 41 of the ATtiny84 datasheet presents the MCUSR Register,

in which the source of a Reset can be identified through the use of flags (bits).

Task.

  1. Your Session 5 supplemental parts kit contains an ACES debouncer PCB. Solder the indicated parts to the board and seat it as an appliance to the DDBv6, so that a falling edge of OUT rests in RESET (digital pin 11; PB3).
  2. Span a bicolor LED across PA2 and PA3.
  3. Create the project, ResetSources.
  4. Making maximum use of the predefines included in the iotnx4.h file and register-level code, add statements to your setup() function that will inspect the PORF and EXTRF flags. Invoke your library's LEDOn() function to show RED for a Power On Reset and Green for an External Reset, triggered by the button debouncer.

6. DDBv6: SoftwareSerial

Until such time as the DDB supports hardware USB-to-Serial communication (Version 8?) we make do with software serial support. The USB-TTL Serial cable from Adafruit that you have been provided with permits your DDBv6 to transmit data to your Arduino IDE's Serial Monitor and Plotter.

Task.
  1. If they are not defined already, add the following definitions to your DDBv6XX.h library,

    #define RXPIN 9
    #define TXPIN 10

  2. A SoftwareSerial object can now be instantiated in the form of,

    #include <SoftwareSerial.h>
    SoftwareSerial ddbSerial(RXPIN, TXPIN);

  3. Confirm the identification of the Reset Sources explored in the previous exercise by writing a specific String to the Serial Monitor.

Concept: ATtiny84 Interrupts

Interrupt-driven programming strategies can provide a more efficient approach for responding to asynchronous events. Chapter 10 of the ATtiny84 datasheet, Interrupts, introduces the MCU's Interrupt Vector Table that appears to the right. The order in which they appear in the Table implies priority should multiple events happen simultaneously.

Concept: ATtiny84 External Interrupt

As can be seen, a Reset event is assigned the highest possible precedence, followed by a (single) External Interrupt (INT0; the ATmega328P has two and the ATmega2560 has eight!), and so on. A design mistake I made on the DDBv6 was to attach the onboard LED to digital pin 8 (PB2). Since this is the same pin that supports the INT0 function, the feature was rendered dysfunctional. In DDBv7, the onboard LED was relocated to digital pin 4 (PA4/SCK) restoring the use of INT0.

In class, we'll temporarily switch back to the UNO/Nano and confirm your register-level coding of its INT0 or INT1 interrupt capability through the use of the debouncer.

Page 71 of the ATmega328P datasheet provides Register level details associated with the ATmega328P's External Interrupt manipulation.


7. DDBv6: Pin Change Interrupt

Chapter 11 of the ATtiny84 datasheet discusses this MCU's functionality with respect to external Pin Change interrupts. Whereas specific bits can be configured for the single External Interrupt INT0 (PORT B.2) to sense rising, falling, change, or none signal conditions, only change triggers a Pin Change Interrupt. However, the good news is that any digital pin can be conditioned as such. The applicable registers, bits, and flags are summarized below.

Task.

  1. Develop simple code to configure your button debouncer to trigger an interrupt on a pin of your choosing, lighting the onboard LED for 500 ms as confirmation.


8. DDBv6: Morland Bargraph v3

With register-level coding skills and a custom DDBv6 library underway we can turn to a familiar friend to strengthen our command of these skills in the efficient manipulation of port bits to create a dedicated MBShiftOut() function.

Design Considerations. In designing the MBv3's minimal 6-pin breakout board there simply was no optimum arrangement that enabled it to be a UNO-compatible appliance. Wherever it is placed it puts an unacceptable strain on the port pin forced to serve as the 5V source. So, given the MBv3's versatility in so many ACES' projects, the ATtiny84's pin breakout strategy accommodated a standard position for the MBv3 on the DDBv6. Click the image to the right to enlarge. The 5V and GND supply pins are positioned correctly to provide the appliance with full power access. The only issue that remains is the non-critical conflict with the onboard LED. This has been addressed in the DDBv7 with its relocation to Pin 4 (PA4/SCK).

Task.

  1. Whereas we typically program with versatility in mind, in this exercise you're asked to do the opposite: hard code registers for maximum efficiency of the MBv3 in the standard position, as shown in adjacent photo. You'll notice the MBv3 appliance in this position spans both Ports A and B in the DDBv6 which will need to be addressed in the register-level code you will be required to develop.
  2. Add the public function void MBShiftOut(uint8_t dir, uint8_t val) to your DDBv6 class which result in the display of the val parameter on your MBv3. Hard code data, clock, and latch bits that correspond to the standard position of the appliance, all within the function.
  3. Develop client code that presents continuous binary counting to confirm.

9. DDBv6: Rotary Encoder

As discussed in class, encoders are devices that can map digital signals to binary form. Rotary encoders can present relative changes in angular position to binary form that can be read by MCU to determine counts, or even rotational speed, when applied over the time domain. Here's a short video highlighting the output of an inexpensive rotary encoder on a KY-040 breakout board from Amazon, Rotary Encoder with Bicolor LEDs.

In the Serial Monitor capture to the right, rotary encoder outputs A and B were configured as pin change interrupts on digital pins 4 and 5 (PD4..5), respectively. The port PIND was read and echoed after one clockwise rotation between detente positions followed by one counterclockwise rotation. The Gray Code sequence is clear as should be the strategy to detect the angular direction.

Task.

  1. Using the instruction and assets provided you, develop Pin Change Interrupt client code that will monitor your rotary encoder in the form of clockwise (increasing) and counterclockwise (decreasing) counts.
  2. Using your MBv3 as the display device echo the encoder count continuously.

10. DDBv6: CharlieStick

  1. References
    1. ATmega328P Datasheet. See Section 36 starting on page 612.
    2. ATmega328P Include file: iom328p.h
    3. ATtiny24/44/84 Datasheet. See Section 24 starting on page 182.
    4. ATtiny24/44/84 Include file: iotnx4.h
    5. Search for evidence within the ATtiny84's iotnx4.h file that confirms the information in the adjacent Data Memory Map graphic.
  2. After digesting the previous references you'll appreciate that the header file simply consists of hundreds of #define compiler directives that provide aliases for the specific AVR MCU registers and bit-within-a-byte numbers.
  3. Last fall, in Project 3.2 you were asked to explore Charlieplexing and tasked with implementing our new charlieplexed SimonStick. as Project 3.2.1. As a followup task, Project 3.4.2 asks that you adapt your previous sketch by maximizing your use of Register-Level coding strategies and other #defines from the header file to have your SimonStick function as a VU meter for the TMP36 temperature sensor.
  4. CharlieStick (Register-Level Coding)
    Note: Both devices are expected to be implemented as DDP appliances. You'll have to think strategically for this.


    Theory JLC Rendering

 

  1. Create a DDP folder within your Arduino sketch folder and condition yourself to placing all of the sketches developed for use on the platform in this folder.
  2. Run through a familiar sequence of devices and high-level programming practices to get acquainted with our new environment. Provide evidence in your first DDP DER entry that you have successfully implemented the following three trials: the single LED blink sketch, the Schaffer Traffic Light, and the Morland Bargraph. For the latter, you'll note that the power supply and digital pins of the ATtiny84 have been broken out in a manner perfectly suited for this device. Be sure to highlight this in your Report. I suggest you showcase the following four Morland Bargraph capabilities,
    1. Simple, recognizable binary sequence or alternating pattern
    2. Shift out 0xFF and demonstrate a 'breathing' bargraph by placing a signal on the 595's output enable pin
    3. Review Adafruit's TMP36 terrific tutorial. Now, what's great about the DDP is that without support of the Serial Monitor, we're (somewhat) blind. However, our Morland Bargraph is an output device that can tell us a great deal if we exploit it correctly. So, wise ACES will, first, familiarize themselves with the TMP36 in a more 'informative' environment. Wire the TMP36 from a breadboard to your Arduino UNO and explore its output with the help of the Serial Monitor. OK, with a better understanding of the device, insert it into a strategic location on the DDP and project the result of an analog reading of the sensor on your bargraph over an appropriate thermal range of your fingers while pinching the device. You can either present the raw readings or tailor it as VU meter with a little math. (map() and constrain() are handy functions for this application as is bit-shifting).
    4. Some other creative and inspiring exercise of your own choosing. Look in your kit and come up with something compelling.

    Finally, pack these four Morland Bargraph exercises into a single sketch with some strong code design decisions. Note, the mark you will receive will be based, in part, on how unique your code is from that of your peers.


DDP: USB to TTL Serial Cable

A solution to the benefit of serial streaming to the Arduino Serial Monitor and Plotter from the DDP comes in the form of a USB to TTL Serial Cable from Adafruit (below, left). The basis for this discovery comes in the form of this instructable from OldArkie in which he describes a similar approach from the ATtiny85. The image below, right (click to enlarge) is of a dynamic application of a thumb joystick in a DDP running a sketch (SerialOutputDDP.ino) that streams the 2D coordinates to a Processing application (CircularTrigFunctions.pde) developed to introduce students to the true origin of the six trigonometric functions: The Circular Functions. USB cable connections to the DDP can be determined by looking closely at the photo. The White 5V wire is not connected.

I'll provide a demonstration in class on the resumption of classes after the March Break 2020. Both sketches are available from DDP's GitHub repository.

Adafruit USB-to-TTL Serial Cable #954 DDP Control over the Processing Circular Function Sketch

 


Terminology

An Appliance is an ACES term for a PCB-based device that is inserted vertically into a SINGLE female header on either the UNO or the DDP. The Schaffer Traffic Light (STL), the Morland Bargraph (MB) and the CharlieStick, are three examples.

A Shield is the conventional Arduino term for a PCB-based device that spans BOTH female headers, horizontally, on the UNO. ACES have adopted this term in reference to a device that spans both headers on the DDP.

In late 2019, two DDP Shields were developed for ACES to continue to develop their MCU prototyping skills. By the end of the term, after working extensively with these two shields, every ICS4U ACE will have the opportunity to add to the inventory of our DDP Shields through the creation of their own, original, Legacy Shield for future ACES to benefit from.

4. DDP: ADC Shield

This Shield exploits the 10-bit Analog-to-Digital Conversion feature of the ATtiny84 (oddly enough, the DIP14 ATtiny84 offers 8 separate ADC channels as compared to the DIP28 ATmega328P's 6.)

  1. Download the EAGLE Files for this Shield and examine them closely. You'll likely exploit these later in the term when you design your own DDP Legacy Shield
  2. Q. How are the signals for the 2×3 female input header arranged?
  3. Q. Considering the other shield components what software technique is employed to present the reading?
  4. After our thorough group discussion of the design and cautions, solder the Shield carefully as some parts are irreplaceable (2mm pitch, LA-301VL).
  5. Review the side-by-side pairing of the DDP base (left) and the ADC Shield below (click to enlarge). The silk-screening will enable you to determine and #define the corresponding port/pin usage. Note. When you create your own DDP Legacy Shield do not overlook the benefits of smart silk-screening to those that follow you.
  6. Develop and confirm your code's A/D conversions for your TMP36 (make sure you confirm the correct orientation) a trimpot, and a voltage divider made from an LDR and fixed resistor.
  7. Your code SHOULD,
    1. employ data smoothing using a history list of AT LEAST 50 readings
    2. inhibit leadings zeroes in the display, and,
    3. include the low-level shiftout function we developed in class earlier in the week
  8. Comment your modular code, extensively.


5. DDP: Intersection Shield

In this Shield segment, our Schaffer Traffic Light (STL) gets a serious upgrade. Watch this clip of the simulation, DDP: Intersection Shield (1:08)

  1. Download the EAGLE Files for this Shield and review the connections thoroughly. Take as much DESIGN information into consideration as you can for your similar Legacy Shield effort later this term. Also, since this Shield is more densely populated than the ADC Shield, there was not as much room for silk screening. You'll have to dig deeper into the EAGLE files to determine the pin assignments. Too many of you did not do this sufficiently in the previous ADC Shield project and wasted time and credit as a result.
  2. Again, the Intersection Shield uses two, narrower-pitched, 7-segment displays (2mm pitch, LA-301VL). SOLDER THESE FIRST, using a FINE point solder tip, taking great care to avoid solder bridges, spills, and leaks.
  3. Develop code to match the video sequence and timing as closely as possible. Stretch your register-level coding skills as far as you can, including the use of the register-level shiftout() function discussed previously in class.
  4. Comment your MODULAR, EFFICIENT, COMPACT code, extensively.


6. DDP: Legacy Shield

ACES' tradition reflects a popular culture trope in which Master Craftsmen Make Their Own Tools. A quick review of the ACES PCB Archive supports this claim. In this latest attempt to enrich the engineering experience of the ACES that follow, you have the privilege of being the first group of Sr. ACES to develop an original set of DDP Shields.

What is unique about this PCB task is the myriad of constraints placed on the design of the PCB Shield, not the least of which are its dimensions. Furthermore, by the time ACES are ready to assemble their DDP Shield, you can assume they have SMD/T experience.

Task.

  1. If you have not done so already, create EAGLE projects from the .sch and .brd files available from our RSGC ACES' Dolgin Development Project repository.
  2. Review these designs and come up with the best idea you can to allow ACES to explore concept(s) that you found particularly compelling. The best designs are typically the simplest, least expensive, most flexible and easily adaptable to the broadest range of applications. Feel free to bounce your ideas off me before or after school.
  3. After settling on your idea, download and copy the Shield files (Intersection and/or ADC) that are a better fit with your plans, remove component you do not need and start designing. You only need to ensure your board outline remains identical, as do the positions of the two 1×8 headers that connect to the DDP motherboard.
  4. Be sure to use the ACES SMD/T EAGLE resources available from the top of our course page to expedite your results.
  5. By the deadline, attach five files (DER.docx, .sch, .brd, .cam, and .zip) to an email to handin under the Subject Line: DDP: Legacy Shield.
  6. Ideas? TTC Line 1 (Coding skill), Breadboard Shield (Prototyping), Sensor Shield (Testing), 0.96 OLED Display, ?

7. DDP: AVR Assembly Language Programming

7.1 References

7.1.1 GPIO Port Summaries

7.1.1.1 ATtiny84

7.1.1.2 ATmega328P

7.1.2 Summary: AVR Assembly Instruction Set

7.1.3 Detailed: Online AVR Assembly Instruction Set

7.1.4 Full Manual: AVR Assembly Instruction Set

7.2 Exercises

7.2.1 Inline (8-bit) AVR Assembly (within the Arduino IDE)
In our first few AVR assembly exercises you will explore how the AVR-gcc toolchain permits the interspersing of assembly language statements amongst Arduino C statements through the use of the asm () macro. This blog offers a primer...The following video provides a good foundation for AVR Assembly concepts in a little more detail than is required at the moment but, nevertheless, is highly instructive: Intro to Arduino Inline Assembly

7.2.1.0. The Fastest! Blink
In a previous exercise you successfully confirmed that setting a bit in an AVR Port's PIN register, toggled the corresponding bit in its PORT register, leading to the fastest way to blink an LED. In this first exercise we'll perform the same task, in assembly language.

Task.

  1. Insert an LED into your DDP spanning A0 and ground.
  2. Within an InlineAssembly folder, create a New Project called BlinkInline.
  3. Within your setup() function , add an asm volatile () macro that declares PORTA, pin 0, for output.
  4. Within your loop() function, add an asm volatile () macro that writes 1 to PINA, pin 0.
  5. Using the builtin delay() function add a 1 second delay between loop iterations.

7.2.1.1. (All Assembly) Delay
A clock cycle is a tick of the MCU's oscillator. The source of these ticks typically comes from the MCU's external crystal or internal RC clock.

As you can imagine, the benchmark measure of the efficiency of any code sequence rests with determining the number of MCU clock cycles (or simply clocks) it takes to execute, not the absolute amount of time the code takes to execute. Courses in your university Comp. Eng, program will require you to explore this this so let's get a simple taste, now. Further reading: AVR-libc Benchmarks

The delay(ms) function is handy, but unproductive, as all it does is waste clock cycles. Nevertheless, exploring an 'All AVR Assembly' equivalent to the delay(ms) function is instructive for our ends. So, although the previous exercise confirmed that inline assembly and high-level C can coexist, this exercise allows you to explore replacing the high-level delay(ms) function altogether through additional assembly instructions inside our loop() function's asm volatile( ) macro. In doing so, we'll also acquaint ourselves with a few more AVR instructions.

Task.

  1. Review the AVR Instruction Summary I've posted online. The last column indicates the clocks for each instruction.
  2. Follow this link for a more comprehensive AVR Instruction Reference.
  3. Q: How many clock cycles does the sbi instruction consume in execution?
  4. Review this handy code generator calculator for wasting AVR clock cycles offered by Bret Mulvey. (Wise ACES will right-click the page and review the Javascript source code to deepen their understanding of these important code techniques) An inspired JS enhancement was made by T. Morland, ACES' 18, (of Morland Bargraph fame) which I'll explain in class. You'll also find this utility by click the DELAY link at the top of our course page, as you'll want to exploit its value, often.
  5. Q: Load the AVR Delay Loop Calculator and go to the last text input box (cycles), enter the number 100, and press go. Select avr-gcc and examine the assembly code. Explain why the assembly code is correct (for this value) in terms of wasting clock cycles. Try additional multiples of 100 up to 800. Any comments? Conclusions?
  6. Complete the entries to generate an equivalent sequence of Assembly instructions as a replacemnt for delay(1000). Again, choose the avr-gcc syntax for now.
  7. Load your BlinkInline sketch from the previous class and remove the call to the delay(1000) function. Copy the auto-generated code from the previous step and insert it into your loop() function's asm volatile( ) macro.
  8. Listen closely to the additional explanations in class to have your code run as expected.

 

7.2.2 Standalone (8-bit) AVR Assembly Coding (within the Arduino IDE)

Reference (unnecessarily complicated but informative, nonetheless): https://rwf.co/dokuwiki/doku.php?id=smallcpus

The Arduino IDE offers painfully few tools for the aspiring assembly language programmer to develop a skill set but it has one important thing going for it: familiarity. Make no mistake, confidence, coupled with steady productivity and reasonable success, are required to sustain interest in the challenge of low-level coding and, so far, you're making SUBSTANTIAL progress.

So, let's keep the hardware task the same (fastest blink of an LED) but strip away the cumbersome " " and \n from inline assembly to write clearer, standalone, AVR assembly code.

7.2.2.1. The Fastest! Blink

  1. Within a folder called StandaloneAssembly, create a first project called FastestBlink.
  2. (Now, this step will seem weird...) Delete ALL comments and code from FastestBlink.ino leaving the file completely blank. (an informative action would be to compile (verify) this empty file and read the diagnostic error messages it produces. Remember, all the code you have ever run in the Arduino IDE operates within the C driver shell main.cpp)
  3. So, if we hope to have any of our own code run within the Arduino IDE, we require, at the very least, both a setup() and loop() function. We'll now provide these functions in Assembly!
  4. Our standalone assembly code will be placed in a completely different file, within the project, with the extension, .S (Note: it MUST be a capital S). Look to the top right corner of the IDE, click on the dropdown button, select New Tab and, in the text box, label the new file, asm.S. (Note: you could call it anything you want but let's keep it consistent for today)
  5. Now, enter the code below in the asm.S. file. The .global assembler directive is one of many that assists the toolchain with the creation of the final executable. Functions in assembly language are simply labels. Furthermore, it should be obvious now that they terminate with a ret statement.
    .global setup
    setup:
    	ret
    
    .global loop
    loop:
    	ret
    
  6. You can now add the familiar assembly statement to the setup function, free from the " " and \n syntax required in inline assembly. Comment appropriately.
  7. Additionally, add the familiar statement to your loop function. Comment appropriately.
  8. For our kill function, a .global directive is not required as this function requires only local access (ie, not visible to other files in the project that will be linked together). Return to our AVR Delay Calculator to obtain assembler code for the body of our kill function that will simply waste 1s worth of clock cycles. Comment appropriately.
  9. Add opening comments within your asm.S file, upload. and admire!
  10. Note 1. The Auto Format feature does not apply to assembly code. You must do this by MANUALLY.
  11. Note 2. EVERY assembly statement deserves a meaningful comment. Get used to it.
  12. Note 3. Compile this code and COMPARE the amount of program storage space it requires to the standard File>Examples>Blink sketch.

7.2.2.2. Schaffer Traffic Light
In this second standalone AVR Assembly exercise we return to the venerable STL to continue to expand our knowledge base of instructions. Setting (or clearing) an individual bit od a PORT is handy, but typically you'll want to affect multiple bits at a time. For these purposes you'll need the in and out instructions.

Place your Schaffer's Traffic Light into DDP pins A2..A0 + GND. (conveniently, the Intersection Shield works just as well for these exercises)

7.2.2.1.1 Version 1

  1. Within your AssemblyStandalone folder create the project STLv1.
  2. Clear the STLv1.ino file and add an STLv1.S tab.
  3. Insert the .global functions setup and loop.

7.2.2.1.2 (Improved) Version 2: AVR Assembly delay(ms) Function

Rather than entering and exiting multiple asm volatile () blocks, Version 2 accomplishes the same result with a single asm volatile () block by replacing the Arduino C delay(ms) function with an assembly function that does the same thing (waste clock cycles).

  1. Save your successful STLv1 project as STLv2.
  2. Review the Mulvey/Morland utility for determining just how many cycles to waste. Since we're exploiting the ATtiny84's internal 8 MHz RC clock, enter the parameters to generate code for a 1s delay (we'll use the avr-gcc version for this sketch).
  3. This auto-generated code introduces you to a few new assembly instructions (ldi, dec, brne).
  4. If this 1s assembly code sequence could be structured to reflect a function, it could simply be called n times to waste n seconds! This will introduce the rcall and ret assembly instructions.
  5. Within a single asm volatile () code block in the setup() function, run the STL continuously for same the 3s-1s-3s delay sequence.

 

Seven Segment Counting

To strengthen your skill set, I have carefully developed an integrated set of increasingly-complex projects based on the DDP and the ADC Shield especially for you; the 2019/2020 ICS4U class. It's imperative that you take the concepts that you have been taught, acquire these skills, and prove to yourself you can handle a degree of complexity.

To start, Using the AVR Assembly knowledge gained so far, in particular our Data and Labels lesson, you are asked to present single digit counting, either on a standalone 7-segment display or, preferably, on your ADC Shield. I have prepared a video of what I expect you to develop:

Seven Segment Counting Support Video

I have broken down the necessary steps below to such a degree that anyone with even the slightest bit of motivation and interest in preparing for the challenges that lay beyond RSGC should be able to fulfill.

Task.

  1. Create a project called Shiftout7Segment.
  2. Within the Program Flash section (.cseg or .text), define a 10-element array of segment maps of the form (0Babcdefg0). This will require the use of the .DB or .BYTE directives.
  3. Declare start and end labels, before and after your array (aka. Lookup Table or LUT).
  4. Your code should assign the start and end labels to the 16-bit X and Y (pointer) registers as I demonstrated thoroughly last class in the Data and Labels lesson.
  5. Next, turn on the active 7-segment display by ensuring ground access for the display, If doing this on a single CC display, simply wire pin 3 or 8 to ground. If using the ADC Shield, the rightmost display as shown is grounded by setting PA4 (which is connected to the base pin of its low-side transistor). These assignments can be determined from theADC Shield's silk-screening.
  6. Your code will undertake a continuous loop with the Z register pointing to the same starting LUT address as the X register and advancing by 1 (autoincrement) until it reaches the Y address. With each iteration, the value from the LUT (pointed to by Z) is shifted out to PORTA using the MSBFIRST direction.
  7. Insert a 1 second delay between digit presentations.
  8. The result is a continuous display of the digits from 0-9, repeatedly, as shown in the video.

Be prepared for Monday in the event you get randomized for a Show&Tell.


PoV on the ADC Shield

This project is a consolidation of previously undertaken AVR skills, investigations, and projects. The first DDP Shield you worked with, the ADC Shield, has a set of four, fully-resisted, 7-segment displays, accessible through the use of the onboard 595 shift register, using a Persistence of Vision (PoV) scheme. The PoV is enabled as the ATtiny84's port pins PA1..PA4 are tied to the respective base pins of the four, low-side NPNs that provide ground access to each of the CC displays, in turn.

Task.

  1. Create the project: PoVontheADC.
  2. Through the use of labels and the .DB (.BYTE) directive, your code should define an 10-element array of segment constants within the .cseg (.text) section, defining the state of the LEDs in the order 0Babcdefgx.
  3. Hard code a value between 00 and 99 into Program Flash with the .db directive (or .byte if in the Arduino) to be displayed on the ADC Shield using your shiftout function from a previous project by the same name.
  4. Shifting out should be undertaken with MSBFIRST if the segments are defined as indicated in the previous step.
  5. The correct DATA, LATCH, and CLOCK equates can be found in a recent post to the ICS4U Conference.
  6. As stated, the PoV strategy is accomplished by repeatedly signaling the base pins of the transistors to pull the CC displays to ground. The base pins are attached to PA1 through PA4.
  7. Document and format your code to a standard that reflects the handouts I've prepared for you.
  8. Bonus: For the motivated amongst you, I encourage you to take this project up a level. I could have asked for a 16-element array of segment constants (0-F), asked you to hard code a value between 0000 and FFFF, and requested a 4 digit PoV display.

Attach JUST two files ONLY: DER.docx and either main.asm (or PoVontheADC.S if you develop within the Arduino IDE) by the deadline.

Pseudocode for this Algorithm...

  1. Define a 10-element segment Lookup Table (LUT) in Flash (same as previous task)
  2. Assign to number the two-digit value (eg. 99) to be displayed
  3. Reserve two bytes of storage in SRAM for the as-yet-to-be-determined tens and units digits of number
  4. Define a register count to hold the tens digit. Initialize it to 0
  5. Assign to Z the address of number
  6. Load r16 with Z (number) with the lpm instruction
  7. Subtract 10 from r16
  8. If the result is less than 0, (the tens digits has been determined: count) advance to Step 10 (brmi)
  9. Increment count and go back to Step 7
  10. Store count in the first of two SRAM storage bytes reserved in Step 3 (sts)
  11. Add 10 to r16 (this is the units digit) and store to the second reserved byte in SRAM (sts)
The two digits have been separated, stored in RAM bytes, and ready for PoV display...
  1. Load Z with the starting address of the LUT
  2. Load r16 with the units digits from SRAM (lds)
  3. Add r16 to ZL to have it point to the correct segment map in the LUT
  4. Load n with the value pointed to by Z (lpm)
  5. Turn off the tens display (DIG3) (cbi) (remember, we need to reduce ghosting)
  6. Call your shiftout function
  7. Turn on the units display (DIG4) (sbi)
  8. Pause for a PoV-suitable interval (see Lesson 69 on our course page)
  9. Load Z with the starting address of the LUT
  10. Load r16 with the tens digits from SRAM (lds)
  11. Add r16 to ZL to have it point to the correct segment map in the LUT
  12. Load n with the value pointed to by Z (lpm)
  13. Turn off the units digit (DIG4) (cbi) (remember, we need to reduce ghosting)
  14. Call your shiftout function
  15. Turn on the tens display (DIG3) (sbi)
  16. Pause for a PoV-suitable interval (see Lesson 69 on our course page)
  17. Go back to Step 12

7.2.2.4. Morland Bargraph Array Presentation

To be developed...

7.2.2.5. CharlieStick

To be developed...

7.2.2.6. CharlieArray

To be developed...

To be developed...

 

 

 

7.3 Standalone Assembly (Atmel Studio 7)

Yikes! :)