Cuis-Smalltalk-SerialPort

This package provides serial port communication to Cuis Smalltalk. The serial port is probably the simplest way to make two machines communicate, it is very common even today, when nothing works probably a serial console can save your day. I repackaged existing code, tested it and wrote this little document. For the origins see the History & Changelog section. CAVEAT. This code was tested only with Cuis running in Linux.

Test & mini HowTo

• Install the package in the usual way, in serial communication it it very frequent to use the '\n', '\t' and '\c' special characters. For this reason I will also load Printf.

Feature require: 'SerialPort'.
Feature require: 'Printf'.

• Then, to do a realistic test, one that mirrors a real life use case for the serial port, you will need some hardware:

  • Two computers, I use Linux in both.
  • 2 USB-serial adaptors. Be warned, not all USB-serial work well together, if you want to be 100% sure it will all work just buy two of the same brand and model.
  • A null-modem adaptor (for example this which I am using right now). Or you can make your own if you are familiar with the soldering iron.
  • On one computer we will talk with Cuis-Smalltalk, in the other we will Python.

• Let's call CP the computer that will comunicate with Python and CC the computer that will comunicate via Cuis.

• This is the connection scheme (made with the powerfull NiCad).

• Plug a USB-serial adaptors in each of your computers and check out the last lines in $> sudo dmesg, you should see the name given to the newly connected widget device, to me it is /dev/ttyUSB0 in both computers.

• Prepare the serial in Python

# in a shell of CP do 
$> python3 
>>> import serial      # if you don't have this package you need to install it
>>> serP = serial.Serial("/dev/ttyUSB0", baudrate=19200, bytesize=8, parity='N', stopbits=1, timeout=None, xonxoff=0, rtscts=0) 

• Prepare the serial in Cuis and send a message. Remember to take a look into SerialPort>>initialize there are defined the default communication settings for a serial port. Most of the times you need to modify only the connection speed, that is what we will do here.

" in Cuis-Smalltalk Workspace of CC do "
serC _ SerialPort new. 
serC baudRate: 19200.
serC openPort: '/dev/ttyUSB0'. 
serC nextPutAll: ('Hello from Cuis, who is there ? \n' printf: {}). 

• Receive the message in Python and send a messagge back

>>> serP.readline()
b'Hello from Cuis, who is there ?\n'
>>> serP.write(b"Hello Cuis, here is Python, what's up ? \n")

• Read the message in Cuis then close the port, rats do not like much snakes.

serC readString .  " => ' Hello Cuis, here is Python, what''s up ? 
' "
serC close.

• That's it! We saw we are able to make Cuis read and write over the serial line with another computer running another programming language.

• Exercise.1. Try to communicate with minicom instead of Python.

• Exercise.2. Try to connect 2 USB-serial to only one computer and e.g. let two Cuis instances it talk themselves.

History & Changelog

• On 10-Dec-2021 I was born as a repackaging of G. Arduino software available here. Mr. Arduino several years ago kindly adapted the existing Squeak code to Cuis.