- Thu Mar 17, 2016 5:28 am
#43388
There seems to be a degree of mystery surrounding the use of the ADC to read the internal supply voltage. Using nodemcu/lua the docs say:
Battery? Whatever. But on further investigation this actually makes sense. Looking at a description of the "esp init data" byte 107 concerns the voltage of PA_VDD and is listed as tx_param37. So I'm thinking this is really more to do with calibrating the radio transmitter circuitry. PA_VDD would then be Power Amplifier input voltage and for proper compliance the supply voltage would need to be known - if not a fixed value, i.e. battery operated.
So, I think it's fair to say that there's more to this than the simple requirement to monitor the supply voltage from the application's standpoint. It may be that any battery operated ESP8266 ought to have tx_param37 set to 0xFF in order for the radio to perform correctly - regardless of whether it will be read by the application or not.
On the ESP8266 there is only a single-channel, which is multiplexed with the battery voltage. Depending on the setting in the "esp init data" (byte 107) one can either use the ADC to read an external voltage, or to read the system voltage, but not both.
Battery? Whatever. But on further investigation this actually makes sense. Looking at a description of the "esp init data" byte 107 concerns the voltage of PA_VDD and is listed as tx_param37. So I'm thinking this is really more to do with calibrating the radio transmitter circuitry. PA_VDD would then be Power Amplifier input voltage and for proper compliance the supply voltage would need to be known - if not a fixed value, i.e. battery operated.
So, I think it's fair to say that there's more to this than the simple requirement to monitor the supply voltage from the application's standpoint. It may be that any battery operated ESP8266 ought to have tx_param37 set to 0xFF in order for the radio to perform correctly - regardless of whether it will be read by the application or not.
