ESP8266 Community Forum

Is there any specific order in which the API function call "system_phy_set_max_tpw" needs to be invoked? Is it known to work at least in 1.5.2 version of the SDK? I tried before and after starting 8266 as an access point, and as a client. I tried setting the power with value "1" as well as "0" to see if I can see a lower signal strength on a Windows/Linux Wifi connect, but I still see full strength for the signal.

ESP SDK API call "system_phy_set_max_tpw" does seem to work. Earlier I was Windows provided tools to detect the signal strength, which I am not sure if I can rely on, at least for my experiments. With two ESP12Es I can at least see signal strength vary between -18dBm to -45dBm for values of 1 through 82 to the API call when the two are very close to each other.

For now I believe this is a non issue for me. I will continue to experiment to learn the characteristics of the ESP12E antennas at the level possible for me. It would still be interesting to hear if anyone else has done similar experiments and have specific values that they can share.

The following is also posted on bbs.espressif.com http://bbs.espressif.com/viewtopic.php?f=7&t=1976

To evaluate and understand the transmit power settings and resulting RSSI values at the remote receive, I have two ESP12e boards placed side by side within an inch of each other. [I have also tried placing the boards such that their antennas are within an inch of each other.]

On the transmitter I invoke "system_phy_set_max_tpw" using value of 1. The receiver reports RSSI values anywhere near -45. When I increase the transmit power to 82 the receiver reports RSSI of values between -16 and -20.

Questions:
1) Are these numbers reasonable and within expected range? For the ESPs are the RSSI values the received power in dBm, or is it just a relative number? What are the min/max expected?
2) For a fixed max power setting of value 82 to the API, why do the RSSI values vary so much even when the two boards are so close to each other (almost touching)?

/**
* set the output power of WiFi
* @param dBm max: +20.5dBm min: 0dBm
*/
void ESP8266WiFiGenericClass::setOutputPower(float dBm) {

if(dBm > 20.5) {
dBm = 20.5;
} else if(dBm < 0) {
dBm = 0;
}

uint8_t val = (dBm*4.0f);
system_phy_set_max_tpw(val);
}