ESP8266 Community Forum

- Tue Oct 20, 2015 1:53 pm #31860 Hi,

I'm using an ESP12-E with SDK 1.4. If I measure VDD using different multimeters I get exactly 3.33V. But using system_get_vdd33() returns 3.5x Volt (the returned value is 3561). I was wondering if I did something wrong. The ADC-Pin is floating and the appropriate settings in the boot.bin is set (otherwise it would not work at all as I understand). I could calculate an offset now, but first I'd like to be sure that I understood everything right. Does anybody have experience in using system_get_vdd33()?

- Tue Oct 20, 2015 6:53 pm #31875 Smoke and Mirrors apparently unless there is a HardWare option to use adc on V+ like some PIC's
From my reading the ADC is 0-1V

- Wed Oct 21, 2015 5:36 am #31897 Hi !

I could calculate an offset now, but first I'd like to be sure that I understood everything right

Same things here with 6 different modules for 'get_vdd33' (better results for 0-1V ADC 'Tout' input )
Needed constated offset : between 0.1V and 0,2V (substracted to the value returned by :

Code: Select allsystem_get_vdd33()

We don't have much informations about Vref ('about 1V' , tolerance ?) !
+ We have no information about (resistive ?) switchable hardware betwwen Vdd and ADC internal input !

- Sun Oct 25, 2015 9:19 am #32240 Thank you for the feedback. I tested with ESP-12, ESP12-E, ESP07, ESP 201 meanwhile and I also observed different offsets on every module. But as far as I can tell: If you measure the voltage with a multimeter once and calculate an offset, this offset seems to apply for a wide voltage-range. So it is fine for my application in a battery-drive sensor project.