Content originally posted in LPCWare by Wenzu on Sun Jul 24 05:59:03 MST 2011
So after a couple months testing on breadboards with the help of breakouts, I've made a PCB for my 1769 project.
In this board, I only use 1x 12Mhz crystal.
There is no 32768khz xtal2.
For some strange reason, when I power up the board from the onboard USB socket -> into the onboard 5v to 3v3 LDO to power the board, the processor refuses to start.
I have to do a manual reset ( RESET_N to GND ) and then the board starts.
When it is already powered up from USB and I re-program from the JTAG/SWD, it starts normally and works normally as if I was still using the original LPCXpresso board and breakouts.
The pins relevant are, as far as I know, all connected properly:
+3v3 : Pins 10, 12, 19, 28, 42, 54, 71, 84, 96
GND: Pins 11, 15, 31, 41, 55, 72, 83, 97
Then also...
1) a 10K resistor from pin 4 TRST_N (pin 4) to +3v3
2) a 10K resistor from pin 17 RESET_N (pin17) to +3v3
Where could I be wrong, and what to test to know if the board is holding in reset for some reason.
Last but not least. Pullups on JTAG are not fitted.
Edit: fitted a 100nF to ground on the RESET_N, to try a delay.... still no joy.
Thanks !!