how to set BLE transmit power above 3dB?

[ea2020]

I have my basic solution working (Adafruit ESP32 Feather to custom iOS application), but am not quite getting the range I want.

esp_bt.h enums the available esp_ble_power_type_t and esp_power_level_t to use when calling:

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esp_ble_tx_power_set(esp_ble_power_type_t power_type, esp_power_level_t power_level)

These suggest that using ESP_PWR_LVL_P9 should result in a +9 dB transmit power rather than the +3 dB default.

BLEDevice.cpp shows that the BLEDevice::setPower method calls the above function and sets the default power (ESP_BLE_PWR_TYPE_DEFAULT) to whatever power level is passed in with the call.

I've tried calling BLEDevice::setPower in many places (immediately after my call to BLEDevice::init, in my server callbacks after a successful connection, etc.). But, I always end up with +3dB of transmit power according the the nRF connect app (range and RSSI values also remain unchanged).

Digging through the IDF documentation, I found the following function:

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 esp_bredr_tx_power_set(esp_power_level_tmin_power_level, esp_power_level_tmax_power_level)

There is a note saying that it must be called after esp_bt_controller_enable and before anything that would cause the RF section to transmit.

Since esp_bt_controller_enable is called in BLEDevice::init, I tried the following:

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BLEDevice::init()
esp_bredr_tx_power_set(ESP_PWR_LVL_N12, ESP_PWR_LVL_P9)
BLEDevice::setPower(ESP_PWR_LVL_P9).

I still only see +3 dB transmit power.

I cannot find a call to esp_bredr_tx_power_set anywhere within the arduino IDE BLE source files (1.0.4/libraries/BLE/src), so I do not know where the default esp_power_level_tmax_power_level is being set.

Does anyone have any suggestions of what I am doing wrong?

If not, can anyone tell me where the +3 dB default value is set so I could at least hack something ugly together to test with +9 dB?

[GYC-Espressif]

Hello. This function is provided by ESP-IDF. And you can use it in following ways.

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1. /**
2.  * @brief  Set BLE TX power
3.  *         Connection Tx power should only be set after connection created.
4.  * @param  power_type : The type of which tx power, could set Advertising/Connection/Default and etc
5.  * @param  power_level: Power level(index) corresponding to absolute value(dbm)
6.  * @return              ESP_OK - success, other - failed
7.  */
8. esp_err_t esp_ble_tx_power_set(esp_ble_power_type_t power_type, esp_power_level_t power_level);

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To set the 9dB tx Power for adv, you can set it as

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1. esp_ble_tx_power_set(ESP_BLE_PWR_TYPE_ADV,ESP_PWR_LVL_P9);

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Thanks.