Revolution Pi Python Introduction
- Dirk Conzelmann
A quick and easy introduction to how to use the RevPi with the Python programming language.
Why Python?
Python is simple and straightforward
Documentation
Start interactive Python shell
python3My recommendation uses the IPython interactive shell as it supports tabbed auto completition
sudo apt install ipython3 ipython3
LED switch with Python
Works like writing a "1" to the location in the process image where the RevPiLED is located
Where is the RevPiLED located in the process image?
Run the following command
piTest -v RevPiLEDAt offset 119
# ledswitch1.py
f=open("/dev/piControl0","wb+",0)
f.seek(119)
f.write(b'1')
f.seek(119)
f.write(b'0')Read or write strings
The devices in PiCtory usually provide byte access to the data. You can test this example by using a Virtual Device 32 Bytes in PiCtory.
We read out the offset of “Output_1” variable. This may vary on your configuration, so be careful here.
pi@RevPi40302:~ $ piTest -v Output_1
variable name: Output_1
offset: 43
length: 8
bit: 0Python example code
def writeString(offset, myString):
f=open("/dev/piControl0","wb+",0)
f.seek(offset)
f.write(str.encode(myString))
def readString(offset, length):
f=open("/dev/piControl0","wb+",0)
f.seek(offset)
my_string_as_bytes = f.read(length)
return my_string_as_bytes.decode()
writeString(43,'Hello World')
readString(43,11)
' Hello WorldVerify the contents of the process image with piTest
pi@RevPi40302:~ $ piTest -1 -r 43,11
72 101 108 108 111 32 87 111 114 108
100
pi@RevPi40302:~ $ piTest -1 -r 43,11,h
48 65 6c 6c 6f 20 57 6f 72 6c 64RevPiModIO
Library developed from the RevPi community
Allows easy use of symbolic names from PiCtory
Installation not necessary, already on the device
Documentation
Switch the LED with RevPiModIO
import revpimodio2
rpi = revpimodio2.RevPiModIO(autorefresh=True)
rpi.io.RevPiLED.value = 1
rpi.io.RevPiLED.value = 0
rpi.cleanup()Python I/O Bit Mirror
import revpimodio2
import time
rpi = revpimodio2.RevPiModIO(autorefresh=True)
while True:
rpi.io.O_1.value = rpi.io.I_1.value
time.sleep(0.02)
revpi.cleanup()Video Tutorials
Also, take a look at our video tutorials about Python
Besides, take a look at the following video tutorials