Programming the Arduino Uno in Flashforth

I originally thought of this framework as similar to the Arduino framework, where one had libraries which contain specialized code for specific operations. While a Hardware Abstraction Layer (HAL) makes sense, creating Libraries in the vein of the Arduino framework, does not. It isn't "Forth-like", in that Libraries aren't the way Forth was designed to work. Or most importantly, as this continues to be a site to help someone program in Forth, the Arduino approach isn't appropriate to developing code in Forth.

A key value of Forth, is that it enables the programmer to deeply understand the processor on which they are working. At times, this can be a detriment, as it takes much more time to translate a datasheet into working code as compared to downloading a library, however, this approach helps you learn how the processor works. This knowledge can be valuable as you continue to work with the processor.

The file m328Pdef.inc is included in this repository to document AATmega328P constants, the file Library/328P_HAL.fs is the Forth version of this, except it will base many of the constants per the UNO as mentioned above.

The ATmega328P datasheet is the ultimate arbiter of register names and usage.

Boards and Microcontrollers

This code is being developed for the Arduino Uno. Also works on the Arduino Nano and the Microchip 328PB Xplained Mini.

Automating serial transfers

In developing code, it helps to automate the mundane tasks, in particular, uploading files to the microcontroller board. As I have several development environments which require such automation, I created a repository specific to the task, CT_build. As in CoolTerm build, as it automates microcontroller upload tasks for C, MicroPython and FlashForth along with reconnecting CoolTerm.

The previously existing utilities folder has been replaced by the up tool in the repository above.

Compiling FlashForth

I have a complete entry, however, I will touch on it here as well. Its beneficial to compile your own version as it allows you to continue to make things more efficient for you. For example, I do the following:

1. Increase the baud rate to 250K
2. Added multiple registers (see below), including the 3 DDRn registers, DDRB, DDRC and DDRD. It's easy to reference the other two registers for each port, off of the DDRn register.
3. Change the prompt, so I know that this is a different version

Steps to Compile

1. Get source

Put the source on your desktop to keep FlashForth repository, clean.

cd Documents/flashforth
cp -r avr/FF-ATMEGA.X/ ~/Desktop/FF-ATMEGA.X/
cp -r avr/src/ ~/Desktop/FF-ATMEGA.X/src

2. Use MPLAB X to create project

Follow the following steps in MPLAB IDE:

1. File -> New Project -> Standalone Project (Microchip Embedded -> Application Project(s))
   1. Device: 328P and Tool: Atmel ICE…
   2. Choose XC8 as your compiler (XC8 2.45 works, 2.46 generates errors)
   3. Browse to Desktop and make the Project Folder FF-ATMEGA.X
   4. Set Project Name: FF and Set as main project (Creates FF.X folder which becomes the main folder)
   5. Finish
2. In the Projects column on the left, right-click on Source Files and add Existing Item ../src/ff-xc8.asm (you will need to click the file drop down and go up one folder, to select src folder then the file ff-xc8.asm)
3. Put the following text in Production -> Set Project Configuration -> Customize -> XC8 Global Options -> Additional Options then click Apply and OK

-DOPERATOR_UART="${OPERATOR_UART}" -nostartfiles

3. Edit files to your needs

ff-xc8.asm

Convert all <.inc> references to “.inc” (include quotes on change). Mikael believes this isn't required, I have yet to find the magic incantation which makes this go away.

# in Sublime Text, Shift-Cmd-F, be sure ".*" is checked for regex search
(<)(.*)(\.inc)(>)
"$2$3"
# Made 3 replacements

Optional Change the following line 5792 (search for FlashForth), it can be anything you want to show up on reset.

# original line
        .ascii    "FlashForth 5 "
# new line
        .ascii    "FF 5 250k    "

Confirm the new text length matches the same spacing as the previous text!

config-xc8.inc

Change the following line 41, this increases baud rate to 250k

# original line
#define BAUDRATE0 38400
# new line
#define BAUDRATE0 250000

registers.inc

Add the lines to look like this, adding the 3 registers for each of the ports, Port B, Port C and Port D. Also adding the registers for the Timer/Counters.:

m_const PINB,pinb,0
m_const DDRB,ddrb,0
m_const PORTB,portb,0
m_const PINC,pinc,0
m_const DDRC,ddrc,0
m_const PORTC,portc,0
m_const PIND,pind,0
m_const DDRD,ddrd,0
m_const PORTD,portd,0
m_const TCCR0A,tccr0a,0
m_const TCCR0B,tccr0b,0
m_const OCR0A,ocr0a,0
m_const OCR0B,ocr0b,0
m_const TCCR1A,tccr1a,0
m_const TCCR1B,tccr1b,0
m_const OCR1AL,ocr1al,0
m_const OCR1BL,ocr1bl,0
m_const TCCR2A,tccr2a,0
m_const TCCR2B,tccr2b,0
m_const OCR2A,ocr2a,0
m_const OCR2B,ocr2b,0
m_const TIMSK0,timsk0,0
m_const TIMSK1,timsk1,0
m_const TIMSK2,timsk2,0

This step is optional, if you don't make these changes, you will need to add references in your HAL.

4.Wiring Details

Description	SNAP SIL	Uno ICSP	Wire Color
NC	1
VTG	2	2	Red
GND	3	6	Black
MISO	4	1	Yellow
SCK	5	3	Orange
RESET	6	5	White
MOSI	7	4	Green
NC	8

Uno Connector

Nano Connector

NOTE: The Nano ICSP pin 1 is diagonally opposite of the Uno pin 1.

5. In terminal

cd ~/Desktop/FF-ATMEGA.X/FF.X
make clean all MP_PROCESSOR_OPTION=ATmega328 OPERATOR_UART=0
cp dist/default/production/FF.X.production.hex ~/Desktop/FF.hex
cd ~/Desktop
# if your using Microchip SNAP and ATmega328P (Uno)
avrdude -p m328p -P usb  -c snap_isp -e -U flash:w:FF.hex :i -U efuse:w:0xfc:m -U hfuse:w:0xdf:m -U lfuse:w:0xff:

5. Load Hardware Abstraction Layer (HAL)

I always load the file Library/328P_ports.fs as my HAL. It adds Uno ports, and AVR words required for pretty much anything that I would do on the Uno. Consider it required for any of the examples. You can use CT_build to load your files, CoolTerm (my strongly preferred serial program) or a serial program of your choosing.

/examples folder

• blink - classic Hello, World example for microcontrollers more
• fsm - finite state machine with extensive documentation
• tasks - example used for benchmarking in this entry
• timing - using the examples in the forth folder, how to create blocking timing loops

/forth folder

The forth folder is a collection of forth files which are part of FlashFort demonstrations written by Mikael N. Please use them as examples as well.

/Library folder

• 328P_HAL - mandatory file required for many of the examples, baseline words and definitions for the Arduino Uno more
• T1_CTC - Timer 1, CTC definitions
• T1_PWM - Timer 1, PWM definitions
• T2_FPWM - Timer 2, Fast PWM definitions more
• T2_ms - Timer 2, 1ms interrupt definitions
• buttons - demonstrates how to use button de-bouncing found in the HAL (328P_ports.fs) and buttons.fs more
• table - table lookup example

Sources

I also write about C, MicroPython and Forth programming on microcontrollers at Wellys.

Other sources of information which were helpful:

• FlashForth Atmega
• Forth & Arduino Outstanding site with tutorials on Flashforth and the AVR microcontrollers
• FlashForth Intro on Wellys