Month: October 2020

Learning FORTH on Arduino

thequietlearner3 Comments
Some output from Nano running FORTH (no command echo)

FORTH is interesting as a language not as ugly and boring as C, yet more lightweight than lisp. For the uno (328PU) ulisp requires 97% of the program store space, and 74% of your dynamic memory, while Arduino-FVM needs 36% of program storage space and 69% of dynamic memory. There is more for me to explore as far as space efficiency goes, but anyway I’m giving FORTH a try.

There are a few different FORTH implementations for Arduino – I was looking for the easiest path to get set-up. I landed on Arduino-FVM simply because it was the first one I found that was an Arduino sketch/library which I load quickly without having to learn anything new about how to upload to the 328. I just had to install the FVM library, and then compile a sketch which gives me the actual interpreter to load on the microcontroller.

https://github.com/mikaelpatel/Arduino-FVM

You can’t really learn the fundamentals of FORTH programming from just looking at Arduino-FVM documentation; so I installed gforth on my Guix desktop computer and used the gforth info page that has nice reference material and an extensive tutorial. Then I looked at the Arduino-FVM source code, which documents the parameters for the arduino-specific words.

This one liner will blink the LED on and off:

: blink true 13 pinmode begin 500 delay 13 digitaltoggle again ; blink

For those total unfamiliar with FORTH, it is sort of like doing programming on a reverse polish notation calculator, but with a larger stack available.

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Minimalist Arduino Board

thequietlearner3 Comments
Atmel 328PU microcontroller with minimal circuitry for 16Mhz operation

I wanted to get a feel for using the 328P without the arduino board, and practice soldering. I used this tutorial:

https://www.arduino.cc/en/Tutorial/BuiltInExamples/ArduinoToBreadboard/

16Mhz operation requires two capacitors, a quartz crystal, and a 10k resistor, as represented above. It is possible to cut down on the circuitry by using the internal 8Mhz oscillator, but I didn’t do that.

Up close view of top of minimalistic 328P board.

In my prototype, to supply power I simply clip 5V and GND leads onto the pads on the sides. The two wires coming out are the UART read and write lines (serial communication).

I plugged it into power and a USB-serial device (the TPE-USBSERIAL from ThinkPenguin) and to my surprise it worked the first time. I had already loaded ulisp on the microcontroller, and was able to run some lisp commands through the serial connection.

I was surprised it simply worked, mainly because of my frightening magnet-wire solder work.

Scary looking magnet wire mess on back of prototype board.

Methinks I might have to use a bigger board next time, or figure out a different approach.