how to use direct test mode in nrf52840?

[mayuri]

Hi all

I want to check my nrf52840 custom certification.i need to do radio test in my custom board.They are asking direct test mode with PSRB9. I m using direct test mode in sdk 15.2.I m unable to send dtm_cmd via UART.Explain step by step procedure it ll be helpful for me.Thanks in advance

[Andreas]

Hi,

 

DTM is supposed to be used with a Bluetooth tester. If you want to  verify that it works the easiest is to use a nRF52840 DK as UART bridge

1. Cut SB40 and SB41 on the DK to cut power to the nRF52840 on the DK.
2. Connect P0.06 and P0.08 to the RXD and TXD pins on your DUT.
3. Connec the DK to a PC using the USB cable
4. Use nRFgo Studio to send valid commands

 

Best regards,

Andreas

[cbd]

I'm a little unclear.

Did you include provision for external test equipment to be connected to your board via UART in order to drive the DTM functionality?

If so is it not working?

[Andreas]

Hi,

 

I am not quite sure what you mean by provision, the application just waits for a valid DTM command (see the Bluetooth spec), it does not care what kind of equipment it comes from. When using a Bluetooth tester you would just hook the tester UART lines up to the UART lines on the DUT, power on and go. You just need to set the tester to the right kind of interface - UART/2-wire, not HCI or something like that.

 

Best regards,

Andreas

[cbd]

Hi Andreas,

It wouldn't be the first time that a custom board has been laid out without regard to certification and so doesn't have any means of hooking up the test equipment to a DUT UART.

I am unsure what the original poster is having difficulty with.

Is their issue, hardware or software related?

Certainly, if they are using DTM example code then they will probably need to remap UART pins and enable/disable others depending on their board layout design e.g. they may need to hold up line to keep the nRF52 powered.

[Andreas]

Hi,

 

My guess would be setup related, this can be a little tricky to get up and running. As you say you either need to layout a header or similar for this, or make do with available lines/TPs/pads. Anything already on the lines would then potentially mess up the UART communication unless the lines are cut.

 

Best regards,

Andreas