[Open_electroporator] pyflex_f401 v0.6 prototype #2 turn on -- USB mass storage problems
john at cibolo.com
Fri Aug 10 19:01:48 UTC 2018
The v0.6 prototype is repaired and running no load all night and now with the kvboard connected and pulling 40 mA for an hour
and all is well. The stronger transistor is likely what it needed, (even though diagnosis was inconclusive since replaced 2 parts
to fix), and problem happened when USB mass storage started doing something after a big 10 second delay from being connected to
USB. At that time, the PA1 output went HI for a yet un-debugged reason. Whenever that happened, the current draw went to 200 mA
and that was enough to wear out a BC857BWT1G PNP transistor rated at 100mA, but now we are using a BC807-40 PNP transistor there
rated at 500 mA.
I'm changing the code to not use USB mass storage now. The only way to access the virtual file system will be using the rshell
program, not USB. Rshell uses the micropython REPL directly to read and write files, (even though it is connected via the USB
port, it does not use the USB mass storage feature).
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