Direct Test Mode - Transmitter Test

[M. David.]

Hey all

For my project, which is using the nRf52840 as a Bluetooth server, I have to implement a test software. This test software has to, among other things, to send on a specific channel. During this the emitted signal is measured by the test infrastructure (RSSI).

As a basis I've been using the functionality the ble_dtm.h header offers. This worked fine for the SDK 15, but I've had to update to the newer SDK17 and now I've problem calling the function:

uint32_t dtm_cmd(uint16_t cmd);

It accepts only a 16 bit command variable and I don't know, how I've to setup this cmd variable in order to have it conform to my call to this function in the  SDK15 version:

dtm_cmd(LE_TRANSMITTER_TEST, 39, 37, DTM_PDU_TYPE_PRBS9);

note: 39 -> channel 39, 37 -> DTM_LEN

Any help would be much appreciated.

Another question is, is there a better approach for this kind of test, or is using the DTM library ok?

Best regards

Samuel

[Håkon Alseth]

Hi,

 

For my project, which is using the nRf52840 as a Bluetooth server, I have to implement a test software. This test software has to, among other things, to send on a specific channel. During this the emitted signal is measured by the test infrastructure (RSSI).

As a basis I've been using the functionality the ble_dtm.h header offers. This worked fine for the SDK 15, but I've had to update to the newer SDK17 and now I've problem calling the function:

Unfortunately, there's a change in the API between these two SDK versions.

The ble_dtm library was changed to match the bluetooth core specification, Vol 6, Part F "Direct Test Mode". This function now takes in the exact data that is expected over the UART 2-wire interface (taken from Bluetooth Core spec v5.2, page 3197):

You can still conform to the similar functionality, but you need to input the cmd as per the DTM bluetooth core specification.

 

Another question is, is there a better approach for this kind of test, or is using the DTM library ok?

DTM is usually used for bluetooth certification, in combination with a upper tester; where it verifies specific RF PHY features and timing that the bluetooth core spec requires. This is different from teleregulatory certifications.

Many people also use proprietary RF modes, in which case the radio_test example (or the radio_test.c/.h files integrated into your application) can be beneficial to use.

radio_test is more versatile compared to dtm, as it also includes proprietary and 802.15.4 RF PHY. It depends on what you need in your application.

 

Kind regards,

Håkon

[M. David.]

Hello Håkon, many thanks for the quick reply. I've taken the approach with the ratio_test exmple, as you've suggested.

A further question in this regard: My hardware is using the ANT pin of the nRf52840 SOC as I/O pin to which the BLE antenna is connected to. I've seen that for the DMT example project, you could select which pin to use, is this also the case for the radio_test example? Put in other words, Can the pin which is used as I/O for the antenna be configured, and if yes how/where, or is it by default the ANT pin. 

[Håkon Alseth]

Hi Samuel,

 

M. David. said:

A further question in this regard: My hardware is using the ANT pin of the nRf52840 SOC as I/O pin to which the BLE antenna is connected to. I've seen that for the DMT example project, you could select which pin to use, is this also the case for the radio_test example? Put in other words, Can the pin which is used as I/O for the antenna be configured, and if yes how/where, or is it by default the ANT pin. 

I'm not sure I fully understand. Do you have a setup where you have a antenna selector switch (an RF switch), and its controlled via a GPIO? If that is the case, you are free to connect this signal to any available GPIO.

 

Please note that the "ANT" pin on the nRF-IC is the RF pin, and its set-in-stone where that is located on the IC.

Kind regards,

Håkon

[M. David.]

Ok, great. That answers my question. Many thanks!