RF transmit power on STM32WB with Zigbee stack

[ABrua.1]

Hello,

The datasheet for STM32WB55RG (DS11929, 3.6.1 RF front-end block diagram, page 22) states that the output power is user programmable:

"In Transmit mode, the maximum output power is user selectable through the programmable LDO voltage of the power amplifier. A linearized, smoothed analog control offers clean power ramp-up."

The figure 5 in reference manual RM0434 shows a Max PA level input to the LDO but I can't find the register to set this value. 

How do I program the RF transmit power on a STM32WB55 ?

Thanks for considering my request.

[Vyacheslav]

tBleStatus aci_hal_set_tx_power_level( uint8_t En_High_Power, uint8_t PA_Level );

/* @param En_High_Power Enable High Power mode - Deprecated and ignored on

 *    STM32WB

 *    Values:

 *    - 0x00: Standard Power

 *    - 0x01: High Power

 *

* @param PA_Level Power amplifier output level. Output power is indicative and

 *    it depends on the PCB layout and associated

 *    components.Here the values are given at the IC pin

 *    Values:

 *    - 0x00: -40 dBm

 *    - 0x01: -20.85 dBm

 *    - 0x02: -19.75 dBm

 *    - 0x03: -18.85 dBm

 *    - 0x04: -17.6 dBm

 *    - 0x05: -16.5 dBm

 *    - 0x06: -15.25 dBm

 *    - 0x07: -14.1 dBm

 *    - 0x08: -13.15 dBm

 *    - 0x09: -12.05 dBm

 *    - 0x0A: -10.9 dBm

 *    - 0x0B: -9.9 dBm

 *    - 0x0C: -8.85 dBm

 *    - 0x0D: -7.8 dBm

 *    - 0x0E: -6.9 dBm

 *    - 0x0F: -5.9 dBm

 *    - 0x10: -4.95 dBm

 *    - 0x11: -4 dBm

 *    - 0x12: -3.15 dBm

 *    - 0x13: -2.45 dBm

 *    - 0x14: -1.8 dBm

 *    - 0x15: -1.3 dBm

 *    - 0x16: -0.85 dBm

 *    - 0x17: -0.5 dBm

 *    - 0x18: -0.15 dBm

 *    - 0x19: 0 dBm

 *    - 0x1A: +1 dBm

 *    - 0x1B: +2 dBm

 *    - 0x1C: +3 dBm

 *    - 0x1D: +4 dBm

 *    - 0x1E: +5 dBm

 *    - 0x1F: +6 dBm

*/

[ABrua.1]

Thank you. I forgot to say I am using the Zigbee stack. I assume from your answer that the TX power is set by the M0 coprocessor and accessible only via the stack's specific API. Your answer hinted that I should look into the ZSDK API documentation (AN5500) where I found the following:

bool ZbNwkIfGetTxPower(struct ZigBeeT *zb, const char *name, int8_t *tx_power)
bool ZbNwkIfSetTxPower(struct ZigBeeT *zb, const char *name, int8_t tx_power)

Unfortunately, I can't find what's supposed to go in the parameter name. I tried to pass NULL assuming they may be a default behaviour. I also tried to pass a pointer to the value 0, because interfaces are refered to by index in ZbNlmeGetInterface().

I would also need to know how to transform tx_power to dBm. Shall I assume the scale is identical to that of the ACI interface?

A google search on the function name lead me to this unanswered thread: https://community.st.com/s/question/0D53W00000LEgFJSA1/how-did-settxpower-for-stm32wb55-run-zigbee

[ABrua.1 · Accepted solution]

After a brief exchange with ST support:

• TX power after reset is 0 dBm
• name must be "wpan0"
• tx_power is the level in dBm, in the range [-20, +6]

For example, to set the maximum tx power:

  if( ZbNwkIfSetTxPower(zigbee_app_info.zb, "wpan0", 6) ) {
    APP_DBG("Max tx power set");
  } else {
    APP_DBG("Error while setting tx power");
  }

[NZube.2]

I used the code in this post to increase and decrease the TXPower setting. I am able to write a value, and read back that value using ZbNwkIfGetTxPower and ZbNwkIfSetTxPower.

However, I am not seeing a resulting increase or decrease when measuring the output power with spectrum analyzer. Is there a reason I am not able to control the power?

Perhaps Zigbee can't be running when this is changed?

I have the SMPS set to 1.9V and 220mA using the following code and verified the SMPS voltage with a mulitmeter, so I believe it is set correctly.

LL_PWR_SMPS_SetStartupCurrent(LL_PWR_SMPS_STARTUP_CURRENT_220MA);

LL_PWR_SMPS_SetOutputVoltageLevel(LL_PWR_SMPS_OUTPUT_VOLTAGE_1V90);

LL_PWR_SMPS_Enable();

I am modifying the P-Nucleo Dongle Zigbee_OnOff_Client_Router example.

I have flashed the stm32wb5x_Zigbee_FFD_FW.bin, version 1.13.2, but version 1.13.1 showed the same behavior

[NZube.2]

I have been able to load the BLE_ptpClient and BLE_ptpServer examples with the stm32wb5x_BLE_Stack_full_fw.bin binaries.

With this configuration, I am able to use the aci_hal_set_tx_power_level() to set a desired power level and see that level reflected in the measurement on a spectrum analyzer. Therefore my hardware setup is valid, and I am not seeing TX power changing in the zigbee demo.

[Vijay_Ingerrand]

Is this applicable if we run 802.15.4 stack in the MCU (STM32WB55) module??. We are setting only RX sensitivity value to the maximum level.

What will be default value if you not set the TX power, As i understand from the datasheet the Tx power level can be tuned from -20dBm to 5.7dBm.