LPC-Link2 through USB Isolator

[lpcware]

Content originally posted in LPCWare by mubes on Wed Oct 07 02:08:30 MST 2015
Folks,

I am trying to use the LPC-Link2 through a USB isolator as a precautionary measure (I'm working with some motor control stuff, so there are decent voltages floating around on the target board, which is in an Alpha state). 

I cannot get the LPC-Link2 to boot in this configuration. I strongly suspect that is because the LPC-Link2 does not detach from the USB bus (and thus get enumerated again) once it's had its firmware uploaded.

There's plenty more investigation I can/need to do (getting proper logs, flashing a 'permanent' Segger image, looking at the USB bus etc.) but I'm on the road at the moment, so I thought I'd ask if anyone else has any experience of this kind of configuration or has any advice to give?

Regards

DAVE

[lpcware]

Content originally posted in LPCWare by mubes on Tue Nov 03 13:27:49 MST 2015
So, just to close this off, I built a few of the JTAG isolators referenced earlier. They work a treat for SWD (at least on a LPC1347...I haven't tried them on anything else yet).  They don't appear to support JTAG or Trace due to the way the plumbing is done, but that's an acceptable restriction for my current use case at least...

I've made a small printable case to keep the thing covered and avoid stray wires causing havoc.  I'll happily upload the design somewhere but the forum doesn't like OpenSCAD files, and the STL is just too big.  A png of the case is attached. If anyone would like them then feel free to drop me a note (or if a moderator wants to upload them, just let me know).

Regards

DAVE

[lpcware]

Content originally posted in LPCWare by lpcxpresso-support on Wed Oct 14 11:32:59 MST 2015

Sorry, the NXP CMSIS-DAP probes are intended to operate at USB high speed. It's rare to see USB hardware in common use with a 12 Mb/s (full speed) limit. And, some CMSIS-DAP probe bridge functions (e.g. Trace) require USB high speed for acceptable performance.

Thanks and regards,
LPCXpresso Support

[lpcware]

Content originally posted in LPCWare by vtw.433e on Wed Oct 14 02:10:53 MST 2015
Instead of flogging a dead horse with the USB isolator, why not use the JTAG isolator as I suggested earlier?

[lpcware]

Content originally posted in LPCWare by mubes on Wed Oct 14 01:21:54 MST 2015
That's a fair point. Here's the enumeration when directly connected (i.e. into the same port, but without the isolator interposed);

LPC-LINK2 CMSIS-DAP V5.112:

  Product ID:0x0090
  Vendor ID:0x1fc9  (NXP Semiconductors)
  Version:1.00
  Serial Number:A000000002
  Speed:Up to 480 Mb/sec
  Manufacturer:NXP Semiconductors
  Location ID:0x14200000 / 4
  Current Available (mA):500
  Current Required (mA):500

....so, the only difference is that it now enumerates as a HS device rather than as a FS one. These isolators are only for FS use and won't run in HS mode due to the tangling that is needed to introduce a HS device.

This obviously leads to the question to the LPCExpresso guys - can LPCLink2 work as a FS device?  It has enumerated as one happily, but that's not quite the same thing

DAVE

[lpcware]

Content originally posted in LPCWare by LessThanZero on Tue Oct 13 17:40:09 MST 2015


Perhaps you can post the enumeration you see when not connected through the isolator? USB 1.x or 2.0 support is really beside the point, except to say full speed is the highest speed USB 1.x offers. Although the LPC-Link2 may have enumerated at full speed, it may not be prepared to operate there. For example, full speed USB has a different HID packet size limit than HID high speed.

LessThanZero

[lpcware]

Content originally posted in LPCWare by mubes on Tue Oct 13 15:09:58 MST 2015
Why do you say it only supports USB 1.x?  I get exactly the same enumeration values in the System Info when I correct it directly as when I connect it via the Isolator....and it does _claim_ to support 2.0 at 12Mbps.

The main thing that's slightly suspicious is that there's a jumper for selecting 1.5Mbps or 12Mbps operation which, I'm guessing, puts the resistor on the correct data leg....if it _is_ just a simple resistor then it's unlikely to disconnect properly, but I'm not sure why a disconnect would be needed on an already initialised device..

DAVE

[lpcware]

Content originally posted in LPCWare by LessThanZero on Tue Oct 13 14:23:40 MST 2015

Your USB isolator apparently supports USB 1.x full speed. The LPC-Link2 CMSIS-DAP probes require USB 2.0 as a minimum, and support high speed. That's why the LPC-Link2 works when you bypass the isolator.

LessThanZero

[lpcware]

Content originally posted in LPCWare by mubes on Tue Oct 13 10:09:49 MST 2015
OK, I've programmed the firmware, but to no avail. Behavior is the same as previously (and it works fine when directly connected).  Is there any logging I can look at about the way the CMSIS-DAP is detected?  In my USB devices list I can see the LPC-Link2 correctly;

LPC-LINK2 CMSIS-DAP V5.112:

  Product ID:0x0090
  Vendor ID:0x1fc9  (NXP Semiconductors)
  Version:1.00
  Serial Number:A000000002
  Speed:Up to 12 Mb/sec
  Manufacturer:NXP Semiconductors
  Location ID:0x14200000 / 4
  Current Available (mA):500
  Current Required (mA):500

I also tried connecting external power to the target (these isolators don't provide a great deal of power) but no dice with that either...

DAVE

[lpcware]

Content originally posted in LPCWare by lpcxpresso-support on Wed Oct 07 05:17:35 MST 2015

---

Quote: mubes

I cannot get the LPC-Link2 to boot in this configuration. I strongly suspect that is because the LPC-Link2 does not detach from the USB bus (and thus get enumerated again) once it's had its firmware uploaded.

---

Assuming you are allowing LPCXpresso IDE to softload the probe firmware, you could instead try using LPCScrypt to program the probe firmware permanently. This would then avoid any potential reenumeration issue.

https://www.lpcware.com/content/faq/lpcxpresso/lpc-link2-debug-probe-firmware-programming

Regards,
LPCXpresso Support

[lpcware]

Content originally posted in LPCWare by vtw.433e on Wed Oct 07 02:35:05 MST 2015
Try isolating the JTAG/SWD instead...
https://www.lpcware.com/content/blog/isolated-arm-cortex-swd-debug-adapter