Setup details to connect nRF51 device to PC via USB/UART using FTDI chip and in DTM

[norbt]

Hello,

I am planning to use the nRF51 device in DTM and was looking for help on how can use it to control via USB/UART connection to PC using FTDI chip. All I want to do is send commands to the nRF51 device in DTM using terminal application like TeraTerm or PuTTY. I am a newbie here so any help is really appreciated in answering the following set of questions:

1. Which FTDI chip is recommended to be purchased for this device?
2. What would be the connection details between the FTDI chip and the nRF51 chip?
3. How to put the nRF51 device in DTM?

Cheers, norbt

[endnode]

Hi norbt,

Basically any of their "Serial to USB" aka "USB-to-RS232-TTL" will work (it typically looks like this and is very affordable). Btw. if you are not on a very very low budget then you will probably get nRF5x DK with SEGGER J-Link OB chip/FW. That has emulated COM port which works like serial link out of the box (in case that SEGGER drivers install as they should). You can then start with UART examples on dev kit and once you feel confident you can port it to another HW (you will always see UART PINs in particular HW header file - e.g. for nRF51-DK it's "examples\bsp\pca10028.h" inside nRF5x SDK - but thanks to flexible "cross-switch" architecture of GPIO peripheral on Nordic's chip you can basically choose any of the PINs and reflect it in your FW). If you wipe nRF5x chip on the DK you can easily plug the Tx/Rx PINs from external board to proper UART PINs on dev kit and use SEGGER J-Link OB COM port straight away (you will safe few bucks for the cable).

If you are planning to add serial port feature to your HW then I recommend to look into FT323R which is widely used and I suppose you couldn't go wrong if you follow the data sheet and reference schematics. I've seen several such custom boards and you just plug USB cable from them to Windows PC and they work like a charm.

For the DTM you can easily recompile ready-made project from SDK path "examples\dtm\direct_test_mode", just make sure that you use project set-up for your chip and board type (if you use custom board then start from DK example with the same IC family and then just change UART PIN assignment in the header file - better create your own header file to preserve the original one dedicated for the DK;)

Cheers Jan