Vmeter only reads upto 3v and then the ADC value loops

erkel

The ADC value at 0v volts is approx 65,536 and then decreases to 0 as the voltage is increased until approx 3v, and then will reset again to 65,536 then decrease again to 0 for 3-6V. So I can only measure over the 3v range.
Trying to change the gain has no affect.
I am using a raspberrypi.
ie
i2cget -y 1 0x49 0x00 w

holofloh

@erkel
This sounds like a poor solder joint at the internal voltage divider (the 11k and 680k resistors).

erkel

@holofloh
I have three of them and they are all the same.

erkel

@erkel
Here is the E2prom data

root@raspberrypi:/projects/battery_blancer/battery_balancer# ./c6
Address 0x00 - 0x0f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x10 - 0x1f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x20 - 0x2f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x30 - 0x3f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x40 - 0x4f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x50 - 0x5f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x60 - 0x6f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x70 - 0x7f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x80 - 0x8f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0x90 - 0x9f: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0xa0 - 0xaf: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0xb0 - 0xbf: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0xc0 - 0xcf: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0xd0 - 0xdf: ff ff ff ff ff ff ff ff 01 1d d9 1d d8 00 00 00
Address 0xe0 - 0xef: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
Address 0xf0 - 0xff: 04 13 e6 13 e2 00 00 00 ff ff ff ff ff ff ff ff

Or is the calibration data wrong and that is why the reading it simply rolling over every 3 volts.

The voltage divider seems ok.
I get ~0.4v at the mid point between the resistors with a 24V supply.

teastain

@erkel Well, seeing as how you are not connecting it to a M5Stack product, but a RPi, what library (driver) are you using?
Also: What language are you programming it in?

erkel

@teastain

Not using any drivers / library abstraction.
Just reading the registers over the I2C bus.

Have tried both Python, C and simply i2cget -y 1 0x49 0x00 w on the command line etc.
Just one layer above bit banging sort of thing.

Does the E2PROM calibration data look correct?

erkel

@erkel
It is working now.
Just a noob issue.
It was the endianesse of the values. it gives the output as expected when converted to little endian, rather naturally reading the value.,