@Joseman should be no problem to add, probably next release and yeah its a handy command.
Is a test-program for the M4-Card available?
e.g. sending 1000000 random-bytes to the M4, when it hungs, i have a hardware-issue.
=>
I have the problem, when the CPC hungs, it can be have different reasons (software faulty, bad-rom-config, CPC-Hardware faulty, M4-Hardware faulty, Power-Problems).
Power: What voltage do I need to measure with a multimeter? (other measurable Parameters?)
There's isnt an actual test program available. There's the diagnostics firmware, but it only checks basics are responding as it should.
But should be easy to create some tests if you want to verify its working proper.
Ie.
10 |httpget,"somethingoftheinternet": rem test CPC->M4->ESP, could also use |time
20 cat: rem test CPC->M4->SD and vice versa
30 goto 10
If you want to check if only the hardware is OK you can of course up and download files, which will test M4, ESP and SD without the involvement of CPC (and dodgy connectors).
For voltage reading, you can read the USB/EXP jumper, that's 5 V input, 3.3V is labelled at the top row, aswell as gnd signals.