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I'm trying to drive a TLC5940 with a brand new RPi Model A+ (V1). I plan to use the Pi's SPI bus to pipe data to the chip, which I've done successfully before using an AVR. The part I'm stuck with is generating a regular greyscale clock for the chip at about 1MHz (the actual frequency doesn't really matter, but it's definitely in the megahertz range).

How can I get GPCLK0 (pin 7/GPIO 7) to output a 1MHz+ clock signal using rpi.gpio in Python? Ideally I'd like to be able to control the frequency.

I found this question about using GPLK0 as a clock for an ADC, however the answer is just "use a crystal" which I don't want to do. Additionally, this question about turning a GPIO to it's alternative output mode didn't help either. I did find an article that uses the one wire bus, and a forum post on how to set up the pin as a clock source in C but nothing in Python.

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RPi.GPIO (as far as I am aware) has no support for setting the clocks.

You could access the raw clock device from Python using code similar to that shown at http://www.raspberrypi.org/forums/viewtopic.php?p=641670#p641670

I have an example standalone C program which sets the clock frequency "Minimal clock access" at http://abyz.me.uk/rpi/pigpio/examples.html#Misc_code. This shows the sort of functionality you'll need to port to Python.

  • Thanks for your answer. I'm going to try using the PWM pins with rpi.gpio and see where that gets me – Bojangles Nov 29 '14 at 7:35
  • @Bojangles As far as I am aware RPi.GPIO only has software timed PWM support, perhaps a few kHz. – joan Nov 29 '14 at 10:14

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