Taking a journey with python3

[KurtEck]

More hints, if the above does not work, then maybe time to add some diagnostics stuff to your code.

Things like: Maybe have the Arbotix blink led once if it receives what you think is a valid packet and blink multiple times if it receives some invalid data.

Or maybe have it echo the data back to you, and have your python code print out what data it received back (probably converted to Hex ascii text).

If it were me, I would hook up logic Analyzer and actually look at the data...

[robotsurgery]

That hasnt made any difference either :/

[robotsurgery]

That hasnt made any difference :/

[robotsurgery]

I mean the LED that shows a connection flashes everytime i try to send so i think its getting there i just dont know whats wrong with what im sending. Ive also been printing stuff as my debug method and i wish i had a logic analyzer lol

[KurtEck]

Again in all cases like this it would help if you actually show your complete programs and maybe pictures of hook up... As such that maybe someone can replicate your program...

On my RPI3, I ran the following: $ python3 ./led_on.py

Where led_on.py is:

#!/usr/bin/env python

import serial
port = '/dev/ttyUSB0'
baud = 38400


ser = serial.Serial(port, baud)
ser.flushInput()
ser.flushOutput()


ser.write(b'0xff')
ser.write(b'0xff')
ser.write(b'0xfe')
ser.write(b'0x04')
ser.write(b'0x03')
ser.write(b'0x19')
ser.write(b'0x01')
ser.write(b'0xe0')
ser.flush()
ser.close()

I then looked at what was output, by simply hooking up my logic analyzer to the FTDI cable.


What you will see is the lines like: ser.write(b'0xff')
Actually output the ASCII characters: 0xff
Not the single byte value 0xff

Hopefully @jwatte knows more here as I see you are on this thread

[jwatte]

You are providing strings to the write() function, so yes, it's writing strings.
However, you have expressed the string constants wrong -- Python uses \x, not 0x, for escape characters.
Instead, do this:

ser.write(b'\xff\xff\xfe\x04\x03\x19\x01\xe0')

[robotsurgery]

Hello,

I am back. I have tried what you suggested to no avail. Since I last replied I have been trying it on a Windows OS to see if it was my serial port but nothing has changed. Originally I was trying it off a Raspberry Pi. Does anyone have any other ideas?

[jwatte]

Your next step in debugging:
Hook up a logic analyzer on the serial output wires, and see what's actually being written.
I recommend a Saleae Logic analyzer of some sort.
(Although it seems they dropped the lowest-cost Logic 4 unit, and also raised prices slightly -- still, they are good hardware with great software support!)

[KurtEck]

Yes - I also second using a Saleae logic analyzer...

FYI - I have a Dynamixel Analyzer that originally was started by user r3n33. Currently I am in the process of adding Protocol 2 support for decoding messages and adding the X series registers... It still is a WIP but getting reasonable...



Also in any thing like this, I recommend posting the actual sources you are trying and anything else needed for someone to reproduce the problem... Which version of python, what type of RPI. What OS...

[robotsurgery]

Yes - I also second using a Saleae logic analyzer...

FYI - I have a Dynamixel Analyzer that originally was started by user r3n33. Currently I am in the process of adding Protocol 2 support for decoding messages and adding the X series registers... It still is a WIP but getting reasonable...



Also in any thing like this, I recommend posting the actual sources you are trying and anything else needed for someone to reproduce the problem... Which version of python, what type of RPI. What OS...

Should a logic analyzer be the way to go? Or could I get another pass-through device like the USB2AX? The code im trying to use is my own from scratch it has been posted earlier in the thread, python 3 as the title says, Raspberry Pi 3 model B, Rasbian.