@robert-hh Concurrent access was my first idea too. To test it: I erased the flash to standard boot and main. Then I preloaded the SD with data. Re-ran the FTP test and it still had the same crashes. Using the FTP server on the device is for me is the easiest way. Otherwise I would need to create a Timer to upload data at regular intervals. To keep data transfer low I would need keep the intervals long avoiding me to have the flexibility of choosing which data I want to download and when. To be honest, I'm a bit disappointed by the eagerness of pycom to attack this problem. The same with my other crash report.

You can also find the expansion board schematics here: https://github.com/wipy/wipy/tree/master/hardware/ExpansionBoard-v1.2

@tcb Thank you!

@VladimirAkopyan there are a couple of expansion boards already which I think are enough for prototyping and even smaller units PySense PyTrack Given the pricing and the fact that the grove connectors while nice to have are not essential whats the value add? You can also use grove with pycom base boards you just need the grove to pin adapter The only thing left is a solar trickle charger but these shouldnt be too hard to get I think i know where you are coming from but just dont think there is an urgent need - maybe there is Andrei