I’ve been playing around with serial comms on my Pi/Picaxe dev rig.
Using Gordon’s wiringPi library makes it easy to open the gpio serial comms port on the Pi and write code with Gambas.
So this post involves writing a simple Picaxe program, and then using wiringPi and Gambas on the Pi to communicate with the Picaxe.
Much of the configuration stuff is described in my previous posts which you can link to from here:-
I am using a PiB2 running Raspbian Jessie, and found I needed the very latest versions/updates for wiringPi and Jessie.
I’m running Gambas v3.5.4 which can be installed straight from the Jessie repository. Dont forget you will need to run Gambas as root, which you can do from a terminal with:-
gksu gambas3
The Picaxe I’m using is an 08M2, but in principle you could use other models/variants.
Picaxe test program
Initially I wrote a simple Picaxe program to send data to the Pi, which looked like this:-
‘Serial comms check
‘===================
‘Send a message at 3s intervals
‘+++++++++++++++++++++++++++++++++++
b0 = 1
main:
SerOut 0,N4800,(“Hi Pi! “,#b0,13) ’13 = CR, 10=LF
inc b0
pause 3000
goto main
Once compiled and downloaded, I used minicom to check that the Pi was receiving the message. So in a terminal:-
sudo minicom -D /dev/ttyAMA0 -b 4800
…which should result in an output like this:-
Welcome to minicom 2.7
OPTIONS: I18n
Compiled on Jan 12 2014, 05:42:53.
Port /dev/ttyAMA0, 09:18:17
Press CTRL-A Z for help on special keys
Hi Pi! 18
…where the “Hi Pi!” number increments every 3 seconds.
If all is OK, its time to write a Gambas program for the Pi.
Using wiringPi in Gambas
After wiringPi has been downloaded, un-packed and built (as described in my previous posts) we need to add declarations to a new Gambas project, which I’ve called: Picaxe2Pi
‘ Gambas class file
Library “/usr/local/lib/libwiringPi” Public Extern wiringPiSetup() As Integer
Public Extern serialOpen(strPort As String, intBaud As Integer) As Integer
Public Extern serialClose(intFileDescriptor As Integer)
Public Extern serialGetchar(intFD As Integer) As Integer
…and declare a few global variables & constants:-
Public iFD As Integer
Const Pi_PORT As String = “/dev/ttyAMA0”
Const BAUD_RATE As Integer = 4800
For more detail: Raspberry Pi Serial Comms – Gambas plus wiringPi
