Alpha Clock Five and serial in Python from a Raspberry Pi

[rolf]

I am attempting to send serial data to an Alpha Clock Five from a Python script running on a Raspberry Pi. I have version 1 hardware, but I have updated it first to stock version 2 firmware and now GPS with the AdaFruit GPS module. I will admit that I am new to Python programming. I was able to use the same cable to upgrade the firmware and run the Processing demos from a Windows PC. The code I have written in Python so far is below. The code runs and the clock resets with no change in brightness…

#!/usr/bin/python
#
# Rolf Mikkelson. 27-FEB-2013
#
import serial
header = chr(0xFF)
# print “header = “, header
myport=serial.Serial(‘/dev/ttyUSB0’,19200)
tosend=”B00111234567″
# print tosend
myport.write(header)
myport.write(tosend)
myport.close()

[Windell Oskay]

If it is resetting, then somehow you must be triggering the Auto-Reset feature, that we use in programming.  So, you need to disable the RTS# line on the FTDI interface.

The solution, I believe, is found here: 

http://iijean.blogspot.nl/2012/05/ftdi-usb-driver-woes-on-debian-livecd.html 

(via raspberry pi forum: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=32&t=6832 )

Explicitly disable the RTS as follows:

myport=serial.Serial(‘/dev/ttyUSB0’,19200, rtscts=1)

 

Please let me know if that fixes it!

[rolf]

I double checked, and my previous attempts were using the EvilMadScientist USB to TTL cable, which has a six pin connector on the TTL end. I tried the Python with rtscts=1, rtscts=True, rtscts=False. Same result on all, clock just resets.

I switched to the AdaFruit cable https://www.adafruit.com/products/954 that has only four pins on the TTL side, and each pin is a separate female pin. I did not connect power, just ground, TX, and RX. Works great now…

[Windell Oskay]

Okay, so there must be something still screwy about the Pi’s USB driver.  Good to know for future reference, at least. 

[rolf]

I have done a bit of programming in Python on a Raspberry Pi for sending data to an Alpha Clock Five. My clock has firmware version 2 with the GPS extensions, so if you have a different firmware, you might need to make changes. Please let me know if you find it useful, comments, corrections, etc…

rolf@mikkelson.info

https://mikkelson.info/AlphaClockFiveSerialRaspberry/AlphaClockFiveSerial.tgz

Files in the above compressed archive:

AlphaClockFiveSerial.py – Library module, imported into each of the other files. If you just run it, all variables are displayed.

brightness – expects a command line parameter of an integer between 1 and 11.

reset – set all parameters back to somewhat sane defaults and sets the mode back to display time.

scroll – expects a quoted string of any length, a delay between updates, and a number of times to loop (between 1 and 99)

bedtime – I plan to add this to crontab to run at 8:15 PM to tell my three year old it is time for bed…

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