I have written some code to simulate some hardware I'm working with and uploaded it to the Arduino board. This code works. I know this, because I get the expected response from HyperTerminal.
However, when I try to connect using PySerial the connection does not error, but I get no response to the commands I send.
Why might this be?
Python code
import serial
def main():
sp = serial.Serial()
sp.port = 'COM4'
sp.baudrate = 19200
sp.parity = serial.PARITY_NONE
sp.bytesize = serial.EIGHTBITS
sp.stopbits = serial.STOPBITS_ONE
sp.timeout = 0.5
sp.xonxoff = False
sp.rtscts = False
sp.dsrdtr = False
sp.open()
sp.write("GV\r\n".encode('ascii'))
value = sp.readline()
print value
sp.write("GI\r\n".encode('ascii'))
value = sp.readline()
print value
sp.close()
if __name__ == "__main__":
main()
NB: the code on the Arduino sends back \r\n
at the end of a response to a command.
HyperTerminal configuration:
I have found that if I increase the timeout to 10 seconds and add a sp.readline()
before I send anything, then I get responses to both commands.
How long is the hardware handshake usually between PySerial and an Arduino or USB RS-232 ports?
How? Using serial inputs is not much more complex than serial output. To send characters over serial from your computer to the Arduino just open the serial monitor and type something in the field next to the Send button. Press the Send button or the Enter key on your keyboard to send.
To check that it is installed, start Pyzo and at the command prompt type in: import serial If it just gives you another >>> prompt, all is good. Checking that it is really working.
Totally non-blocking.
pySerial includes a small console based terminal program called serial. tools. miniterm.
Can not verify this but it could be that you try and read before there is any data there, thus you get no reply back.
To test this you could try and poll until there is data
value = None
while not value:
value = sp.readline()
print value
Edit
The Arduino will reset when you open a serial connection, any data written during bootup will likely go to bit heaven. You could use a sleep for 2 seconds (could not find the exact time it takes, will likely vary anyway) before you do any reads/writes.
Alternatively you could write to it until you get a response back, after you get a return you start doing "real work".
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With