STM32WB55 Formula for converting RAW RSSI value in dBm

[DLan.1]

Dear Sir,

I'm new to STM32WB55 and using STM32CubeMonitor-RF.

We see the value of RAW RSSI from the Value parameter of Command Complete of ACI_HAL_READ_RAW_RSSI in STM32CubeMonitor-RF and it results in the RSSI dBm.

Such as:

(RAW RSSI) --> (RSSI dBm)

0x000006 --> -107.00 dBm

0x000007 --> -107.00 dBm

0x00000A --> -106 dBm

0x00000B --> -105.00 dBm

0x000012 --> -103.00 dBm

0x000014 --> -102.00 dBm

0x000017 --> -100.00 dBm

0x00001C --> -98.00 dBm

0x00001D --> -98.00 dBm

0x000021 --> -97.00 dBm

0x000024 --> -97.00 dBm

0x000029 --> -96.00 dBm

...

0x0001A9 --> -75.00 dBm

May we ask you about the formula for converting RAW RSSI value in dBm? Thank you.

Sincerely yours,

David 

[Andrew Neil]

is there nothing in the datasheet about this?

or the documentation of ACI_HAL_READ_RAW_RSSI  ?

[DLan.1]

We noticed the description in an5270 adhere:

This command of ACI_HAL_READ_RAW_RSSI returns the raw value of the RSSI

and an5378 for Figure 10. ACI_HAL_READ_RAW_RSSI in STM32CubeMonitor-RF packet rate exchange configuration.

We can see the ACI_HAL_READ_RAW_RSSI Command Complete returns the raw value of the RSSI and STM32CubeMonitor-RF performs an RSSI dBm measurement.

Is there datasheet about the Formula for converting the RAW RSSI value in dBm? Thank you.

Sincerely yours,

David

[Sean Park · Accepted solution]

  int32_t rsi_dbm;
  uint32_t rssi_int16;
  uint32_t reg_agc;
 
   // extract the data rssi_int16 + agc
   rssi_int16 = ((rssi_level[0]) >> 16) & 0xFFFFU ;
   reg_agc = (rssi_level[1]) & 0xffU;
 
  // check if rssi is too low
   if((rssi_int16 == 0U) || (reg_agc > 0xbU))
   {
     rsi_dbm = 127 ;
   }
   else
   {
       rsi_dbm = (int32_t)reg_agc * 6 - 127 ;
       while(rssi_int16 > 30U)
       {
         rsi_dbm += 6 ;
         rssi_int16 = (rssi_int16 >> 1) ;
       }
 
      rsi_dbm += (int32_t)(uint32_t)((417U*rssi_int16 + 18080U)>>10) ;
   }
  
   // result is in rsi_dbm ;

Ex) RSSI Level : 0x0701BF

rssi_int16 = 0x01BF (lower 2 bytes of RSSI Level value)

reg_agc = 0x07 (High 1 byte of RSSI Level value)

result -> -33.00dBm

You can refer to the above formula.

[Andrew Neil]

@Sean Park​ - even ST Employees don't know how to properly post source code to their own forum? :\

[Sean Park]

I'm sorry. thanks for pointing out

[DLan.1]

Sincerely thank you for your kind solution.

Sincerely yours,

David

[Andrew Neil]

@DLan.1​ - Please mark the solution:

[DLan.1]

Dear Sir,

Thank you for your kind help.

[DLan.1]

Dear Sir,

Thank you for your kind help.

Sincerely yours,

David