Can DTM on nRF52840 be controlled by SPI interface?

RE: Can DTM on nRF52840 be controlled by SPI interface?

Sigurd — Wed, 29 Nov 2017 16:13:36 GMT

Yes, UART is the de-facto standard. Please take a look at the Bluetooth Core Specification Core version 5.0, page 2773:

Direct Test Mode shall be set up using one of two alternate methods:

over HCI (as defined in Section 2) or

through a 2-wire UART interface (as defined in Section 3)

Each DUT shall implement one of the two Direct Test Mode methods in order to test the Low Energy PHY layer.

All DTM test software is based on this, and DTM testers, such as the Anritsu MT8852B uses UART. You only need 2 GPIO pins to do UART DTM. Creating a non-standard SPI wrapper to do DTM testing does not seem very advantageous. All authorized test lab that does BLE certification uses UART/HCI.

RE: Can DTM on nRF52840 be controlled by SPI interface?

JPierpont — Wed, 29 Nov 2017 15:50:53 GMT

Thanks for the explanation Sigurd. Since we have SPI already in place it would seem advantageous to command DTM over this, however I do not see any testers that support SPI. Are you aware of any or is UART the de-facto standard for DTM?

RE: Can DTM on nRF52840 be controlled by SPI interface?

Sigurd — Wed, 29 Nov 2017 15:37:07 GMT

Hi,

Yes, The nRF5x have flexible GPIO mapping, so all pins can be individually mapped to interface blocks for layout flexibility. You can therefore use any free GPIO pin you have on your board for UART(E).

The nRF52840 have 2 UART(E) Peripherals. The first one can be configured to be used either with or without EasyDMA(either as UARTE0 or UART0), while the second one can only be configured with EasyDMA (UARTE1). The 2 UART(E) Peripherals each have its separate instance. See the Instantiation table here.

RE: Can DTM on nRF52840 be controlled by SPI interface?

JPierpont — Wed, 29 Nov 2017 15:30:55 GMT

Hi Sigurd, we are using SPI interface in our production firmware. Can we add an additional UART interface to be configured in the nRF52840 dedicated for DTM using GPIO pins? - Thanks, J

RE: Can DTM on nRF52840 be controlled by SPI interface?

Sigurd — Wed, 29 Nov 2017 11:39:44 GMT

Why not use the UART ? The purpose of DTM is to test the operation of the radio at the physical level. Please read the DTM example project documentation here, and after that please take a look at our application note about DTM here.

RE: Can DTM on nRF52840 be controlled by SPI interface?

endnode — Wed, 29 Nov 2017 07:32:03 GMT

Theoretically yes, it's just not defined and not implemented in any example. But surely if you have some upper tester which will know how to run DTM commands over SPI instead UART then you can modify DTM FW examples from nRF5 SDK to communicate over SPI.