Weekly Dev Call of February 6, 2017

Here are the dial-in details

Topics today:

You mentioned WS2811 LEDs in the dev call. There is a library called OctoWS2811 that implements the WS2811 LED protocol for the teensy board. It uses DMA to talk to the LEDs with almost zero CPU usage. I think the implementation is really clever.
More details about it on: https://www.pjrc.com/teensy/td_libs_OctoWS2811.html#tech

Thanks @timoski; that’s the DMA technique I was talking about. I just need to figure out whether I can fit it into the available DMA and PWM resources of the Pixhawk FMU. There should also be a way to do it using only a single DMA and PWM channel, but it looks like it would require some cleverness to avoid using too much memory.

@Mark_Whitehorn, I think this is very much feasible. Although I know of no PX4 port, Bitcraze’s Crazyflie firmware runs a strip of WS2811 on an STM32F4 alongside flight control using a single timer and DMA count/compare. The transfer isn’t very memory efficient, but I think they get away with it be only sending partial sequences and redoing the transfers on completion interrupt. Look forward to seeing any progress on the PX4 side for this.