neděle 8. února 2015

RasPi extension board

As promised, a picture of the extension board that will become a center of the RasPi node. Arduino Pro Mini in the middle, surrounded by RF24 module connected to SPI.0 of RasPi, the flat cable to RasPi GPIO header, a display (and buttons) connector with attached display, power supply part with KIS-3R33S, and another RF24 connected to Arduino. The empty socked next to Arduino will host PCF8574P I2C expander (when it arrives from China) that will take care about buttons (if any) and other low speed stuff.To test the display, I used Adafruit ILI9341 Python library, and it worked fine. I rewired the thing a bit and did not test it since, but I assume it should work, or could be fixed if it doesn't.
I had some major issues with the RF24 module - it did talk to RasPi, but did not receive any packets. I spent a few hours trying pretty much everything, and in the end added some tantalum caps directly to the module pins. That helped, and I hope it was the only problem. I added a few capacitors here and there, and one 1000uF is hidden under Arduino... the whole module has so much juice it can run by itself now.
The CR2032 module stopped with around 2.45V. Unfortunately it was snowing overnight, and the snow melted so I retrieved the module in the morning, dripping wet, and reporting voltages around 4V - the water bricked the 1M24 resistor, fooling the divider into thinking there's much higher input voltage. Anyway, the battery now shows 2.94V without any load. I'll continue the experiments in upcoming days.

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