direct test mode : TX power commands

Question

Dear community, 
 I'd like to report a problem on the Direct Test Mode software provided in nrf51 SDK v6.1.0. 
 In this mode, 2-bytes commands are transmitted over the serial port, and interpreted by the DTM software, as follows :
[code: 2bit] [frequency: 6bit] [length: 6bit] [payload: 2bit] 
 This works fine for standard Tx/Rx/reset commands.
However, for more specific radio power control ("Tx power") commands, the above 'frequency' field is used to store the power value, and copied directly into the NRF->TXPOWER register. 
 Unfortunately, this does not work, as expected, because : 
 
 the TXPOWER register data format is 8-bit signed, so 6 bits are not sufficient to code the full range [-40 ; +4]. 
 we could use the 'code' field bits to send 8-bit commands, but in the current state, DTM does not support this format. 
 
 I'm testing a patch to fix, and will be able to post it if necessary.
Your thoughts are welcome ！

Jean-Louis Bonnaffé · Accepted Answer

OK, so if anyone is interested one day, this patch will add support for vendor-specific commands that need 8-bit wide 'frequency' field. 
 One practical example: I want to set NRF51822 radio power value to -30dBm. The TXPOWER register's value is a negative 8-bit value, so DTM won't handle it (it will read the 6 LSB, then cast them as uint32_t). 
 After applying the patch to
${SDK_PATH}/nrf51422/Board/nrf6310/direct_test_mode/main.c, you can send the following 2-byte command : 
 
 [bit 15-08] TXPOWER : 0xD8 (-30dBm) 
 [bit 07-02] LENGTH : 0b000010 (2 bytes) 
 [bit 01-00] PAYLOAD : 0b11 (vendor-specific) 
 
 In bash for example: 
 
 $ echo -ne '\xD8\x0B' > /dev/ttyUSB0

direct test mode : TX power commands

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