SWD with NXP LPC11C22

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Richard Harvie

• December 20, 2013 16:32

I'm trying to connect SWD to a 11C22 M0 chip with crossconnect original + SWD adapter without any luck.

CPU appears to be running - I can erase / program it with flash magic

On CrossStudio, I get  'Cannot set debug register'. Explore window shows no devices..

 

Any ideas what I'm doing wrong? Are there any other pins I should be controlling to enable SWD??

 

Connections are (on the 10w SWD)

Pin1 = 3.3V

Pin 3/5 = GND

Pin 2 = SWDIO (pin 39 on cpu)

Pin 4 = SWDCLK (pin 29 on cpu)

Pin 10 = reset (pin 3 on cpu)

 

Also have an external 6MHz clock into the CPU, but I believe that this CPU will use its internal 12Mhz RC clock until told otherwise.

I've double checked cabling. I can see 4 bursts of SWD data using an logic analyser, but being single wire I can't tell where it's coming from.

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  Richard Harvie

  • December 20, 2013 18:08

  Turns out disconnecting the 6Mhz clock made it work.. Not sure why yet..

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  Richard Harvie

  • December 30, 2013 11:37

  Further investigation shows that the CPU is running quite happily with an external clock input (SYSPLLCLKSEL_Val=1, flashing LED etc), just SWD doesn't work when connected.

   

  For now I'll debug with internal RC, and swap to external clock on release.

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