lpcware

1769 refuses to start

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
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 !!

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