When I received it months ago it seemed DOA but then life caught up and I had to deal with more pressing matters.
When I resumed checking it out last week it seemed to at least power up and after some poking I got it to work about right.
During these days it was mostly on all the time, either with the USB attached or not (I used a LiPo from Sparkfun for this guy).
Last night I left it with the USB plugged in to recharge the LiPo.
And then this morning it stopped powering up altogether when I cycle power.
Well, not quite, actually: from time to time it would power up and boot ok, every 40th attempt or so but then only after some time off.
But most of the time I switch the power on and it does not boot. Everytime, now, in fact.
- The USB LED does not switch on (my code switches it off as soon as the uSD is done configuring but I should still see it, and then I use it to indicate activity)
- Nothing goes to the console - the RS232 and the USB are on the same laptop, therefore I rule out ground loops as a cause for damage.
- If the USB is plugged in, the device does not enumerate
- The LiPo was properly charged (the charger LED still lights up when I plug in the USB).
- 3V3 is present and stable when the switch is on.
- The RST signal is not stuck, I could see it going up and down as I press the button.
- The clock is more difficult to check but I have a hunch it works just fine by looking at the signal on the caps next to the oscillator, but mostly because when I power up the unit in ISP, flash magic can access the LPC2148 and reprogram it which would not be possible without a working clock.
Programmed all right.
Now I don't know any more where to go.
The only things I can think of are:
- If the PLL fried for some reason - the ISP probably does not use it.
- Maybe the ISP runs on the 32kHz, and then my problem is my clock.