nrf52840dk Jlink OB USB cdc offsets 1 character

[rfleming]

I have read through similar posts, though none seem to talk directly about the DK and the JLink OB (SAM IC) missing bytes itself.

To start off with, I have created a basic console application on NCS v1.8.0 on my nrf52840dk. Utilising the USB CDC for ease of connection, this removes the need for an external uart interface.

The console app itself seems largely to work because I use the same api calls and configurations on the nrf9160 on a thingy91 board (specifically not on the nrf52840 on the thingy91...for various reasons just go with it ^^). First noticing that my console couldn't handle the data that was being sent, I started echoing the hex of the byte received back over the console and noticed that it was always out by 1 character.

Scoping location:

In the end I used my oscilloscope and scoped the output from the SAM IC to the input to the nrf52840 on P0.06 and TP4. Leaving my probe on TP4 and doing a fresh power up I note the following:

1. No default output occurs from SAM -> 52840
2. Open Com port with baud @ 115200, no hw control IOs set
3. Send 1 byte through 0x30
4. This comes up correctly as 0x30 on the scope
5. send through 0x31, this reads as 0x30 on scope
6. send through 0x32, this comes up as 0x31
7. send through 0x32, this comes up as 0x32
8. send through 0x33, this comes up as 0x32
9. and repeat

It appears as though there might be a bug on my nrf52840dk jlink OB IC. I am unsure how/when this occurred as I believe it used to work just fine and this is a recent acquisition. on my DK, the SAM IC has the following information printed on it:

• PCA10056
• 2.0.1
• 2020.13
• 683824488

I do not believe that I updated my SAM IC's firmware at any point, though if I did, what would be the procedure for reflashing this IC? I do have an external JLink programmer and the special 2x5 1.27mm spring pin cable for programming it if required.

[JONATHAN LL]

Hi,

Do you have a different DK to test and probe to see if it acts differently? just to confirm that it might be a JLink OB IC issue.

I will look at this case and get back to you with more questions and answers, early next week. 

Regards,
Jonathan

[rfleming]

Unfortunately, I only have the 1x nrf52840dk. It is also the only Nordic kit I have that contains the onboard J-Link IC. All others require the external programmers.

Edit: Also note I have Atmel Studio installed with an Atmel ICE programmer, so if required I could simply write any new/old binary with that. If, of course the security IO is not set etc. I know this is a competitors IC of sorts, so it could be a bit of a conflict and I am happy to reach out to Segger directly if that's more appropriate.

[JONATHAN LL]

Hi,

The Atmel ICE programmer will not work, as far as i am aware it does not support nRF products, so you will have to find some other tool to use it i belive. 

It has ben asked before here: (+) nrfjprog supported SWD devices - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com) 

Can you try to use a different interface, bypass the debugger chip. Cutting SB50 to 53 will give you access to the MCU lines so you could use something else then the onboard programmer chip. 

Regards,
Jonathan

[rfleming]

Hi Jon,

In this case I was referring to programming the Atmel (Microchip) based ATSAM3U2CA - the IC chosen to use as the Jlink OB. I do believe this IC is supported by the Atmel ICE. However, I do also have an external JLink Pro that I could use to reprogram the Onboard Jlink OB as well. Though I don't know what the best way to go about it. Does the OB for instance, have a bootloader that I could simply upgrade/reflash its firmware over USB? Or is it better to reflash the chip entirely?

As you mentioned though if I don't come to a solution, I may just bypass the USB CDC convenience and use and external USB to Serial converter.

Cheers,

Ryan.

[JONATHAN LL]

Sorry for the misunderstanding, 

Yes the interface MCU has a bootloader on it, you can access it by holding the reset button while powering on the kit, does show up as a BOOTLOADER drive.


then its drag and drop.

Regards,
Jonathan