LPC Microcontrollers中的主题 Re: SW port damage

SW port damage

lpcware — Wed, 15 Jun 2016 19:11:29 GMT

Content originally posted in LPCWare by IanMellor on Tue May 19 10:17:56 MST 2015
Hi, I'm having some problems programming LPC4337 (144 pin) on our custom PCBs.
We are programming using the SW interface.
They used to program OK but 2 have now failed.
The error we are getting is: No Cotex-M SW Device Found
We did get other errors earlier on including memory write errors (I think).
We are able to talk to the device using the serial debugging port (using Flash Magic)
I think the error may be caused by damage to the SW port.
Attached is the schematic of our interface.
We are using Jlink but uLink2 doesn't work either.
We have a Keil MCB4300 which programs OK so this seems to verify that the Jlink and connector are OK.
Attached are 3 traces I have done using a scope on SWDIO/SWCLK and RST.
Also here are the steady state levels on the boards:

UnitSWDIORESSWCLKRESFile
PCB12.12V10K1.38V66RTEK00002
PCB20.41V6.4K0.04V266RTEK00003
MCB43000.8510K0.04V10KTEK00004

This is a 3.3V system.
As you can see the SWDIO doesn’t seem to be able to swing fully.
From the resistance to GND readings (RES) the inputs are obviously damaged.
Could this be caused by ESD damage or plugging in/out the programmer?
Any suggestions or info on failure modes would be great thanks.

Re: SW port damage

lpcware — Wed, 15 Jun 2016 19:11:30 GMT

Content originally posted in LPCWare by R2D2 on Tue May 19 12:26:22 MST 2015

Quote: IanMellor
Attached is the schematic of our interface.

Then your problem is missing hardware :D

Re: SW port damage

lpcware — Wed, 15 Jun 2016 19:11:31 GMT

Content originally posted in LPCWare by IanMellor on Tue May 19 13:33:12 MST 2015
It would probably work better with no hardware than what I've just attached..... ;-)

Re: SW port damage

lpcware — Wed, 15 Jun 2016 19:11:31 GMT

Content originally posted in LPCWare by R2D2 on Tue May 19 14:38:44 MST 2015

Quote: IanMellor
It would probably work better with no hardware than what I've just attached..... ;-)

Perhaps that's a good idea, there are boards without all this SWD pull-ups and pull-downs :)

Re: SW port damage

lpcware — Wed, 15 Jun 2016 19:11:32 GMT

Content originally posted in LPCWare by LessThanZero on Tue May 19 17:56:13 MST 2015
Many of the newer chips have internal pull-down resistors which makes the external hardware unnecessary.

Re: SW port damage

lpcware — Wed, 15 Jun 2016 19:11:33 GMT

Content originally posted in LPCWare by LessThanZero on Tue May 19 17:56:15 MST 2015
Many of the newer chips have internal pull-down resistors which makes the external hardware unnecessary.