[Pecan Pico 8] Solar powered camera tracker for balloons

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A319
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[Pecan Pico 8] Solar powered camera tracker for balloons

Postby A319 » Sun Sep 11, 2016 5:07 pm

Good afternoon.

As announced in the Pecan Pico 7 thread, I've got my Pecan Pico 8a ready. Thank's to Bob (FXCoder) who helped me, to find last minute bugs on the PCB. Unfortunately I already found the first error. But I expected that to happen on the first revision.

This time I let the PCB's produce in Germany, because I needed them in time for the UKHAS Conference 2016 in Cambridge, UK. So far I rushed to adapt the code from the Pecan Pico 7 code for some hours, so I was able to present the new module on conference basically.

I figured out, that there are some startup glitches. The board does not startup when the camera is connected from beginnning. But this could be also an error of this particular PCB. I will investigate this later again.
With no camera attached the board doesn't start up accasionally as well. I have a guess what the cause could be: To boost the voltage at the microcontroller, there's another resistor connected to the feedback of the Stepdown regulator. If this resistor is pulled low (by the STM32), the VCC bus voltage will increase to 3.0V. So you can transmit with more power (20mW => 60mW). But if the resistor is pulled up, the voltage may drop and the STM32 will stop working. While I call chHalInit() and chSysInit() in the boot process, the voltage drops multiple times for less than a millisecond (spikes) to 1.6V. And I think that might be the problem.

I will post some pictures of the module later. At the moment I'm still waiting for my flight back at London Heathrow.

All components of this project are open source and can be accessed on Github: https://github.com/DL7AD/pecanpico8 (Hardware and Software)

Regards Sven

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