LPC MicrocontrollersのトピックJTAG problem with LPC1776

JTAG problem with LPC1776

lpcware — Wed, 15 Jun 2016 17:34:15 GMT

Content originally posted in LPCWare by Alex on Mon Oct 07 04:44:40 MST 2013
Hi,

I've designed an UART to ethernet converter using an LPC1776.

The boards are just coming out of factory and I'm trying to program the firmware into the LPC. But unfortunately JTAG doesn't work.

I'm using a SEGGER JLINK hardware revision 6.0 and IAR embedded workbench 6.5

I get two different errors when I try to connect to the LPC1776:
Mon Oct 07, 2013 12:27:26: Could not measure total IR len. TDO is constant high.
Mon Oct 07, 2013 12:27:26: Warning: At least one of the connected devices is not JTAG compliant (IEEE Std 1149.1, 7.1.1.d, IR-cells). (NumDevices = 4, NumBitsSet = 0)

I monitored the JTAG lines with my scope to verify the hardware is OK. The signals are looking quite well and all connections seem to be ok but the data on the TDO line makes no sense for me.

I attached a screenshot of my scope and a part of the schematics of the device.

Maybe somebody has got an idea.

Thanks!

Best regards,
Alex

Re: JTAG problem with LPC1776

lpcware — Wed, 15 Jun 2016 17:34:16 GMT

Content originally posted in LPCWare by Dragonheart77 on Mon Oct 07 10:08:55 MST 2013
Hi,
try a pull-down on TCK (also they use a pull-up in the user guide) and a pull-up on TDO. They are used in evalboards, so do I and I have no problems.

Re: JTAG problem with LPC1776

lpcware — Wed, 15 Jun 2016 17:34:16 GMT

Content originally posted in LPCWare by lpcxpresso-support on Mon Oct 07 15:32:46 MST 2013

Here's FAQ regarding JTAG/SWD debug connections.

http://support.code-red-tech.com/CodeRedWiki/HardwareDebugConnections

Regards.

lpcxpresso-support

Re: JTAG problem with LPC1776

lpcware — Wed, 15 Jun 2016 17:34:17 GMT

Content originally posted in LPCWare by Alex on Tue Oct 08 05:24:30 MST 2013
I added the pull up and pull down resistors but it's still not working. I also verified the resistor connections to make sure they are attached properly.

Edit:
Finally found the reason...

The initialization code switched to main oscillator but the main oscillator was not enabled at that time...

Has anybody an idea to access a device that has been programmed in that way?

Best regards,
Alex

Re: JTAG problem with LPC1776

lpcware — Wed, 15 Jun 2016 17:34:17 GMT

Content originally posted in LPCWare by Rob65 on Tue Oct 08 22:38:35 MST 2013
The boot loader is always executed first, so whenever something like this happens in your code you still have an escape.
Pull down pin 2.10 (ISP) and then reset or power up your device. This will leave the device in the boot loader giving you the option to program it through JTAG/SWD or the UART0 (using a tool like FlashMagic).

See also chapter 32 "LPC17xx Flash memory interface and programming" in the user manual, there the whole boot/programming procedure is described.

Regards,

Rob

Re: JTAG problem with LPC1776

lpcware — Wed, 15 Jun 2016 17:34:18 GMT

Content originally posted in LPCWare by Alex on Wed Oct 09 00:19:55 MST 2013
Great. Thank you.

Regards,
Alex