First version of obniz development board tends to have a ripple noise on it’s vcc line.
It depends on USB adaptor. But with most USB adaptor, an obniz will have ripple.
obniz can work with that’s noise. It is little noise but A/D result may be affected. Because obniz A/D result is adjusted regarding VCC.
And If you are using analog temperature sensor, then you will get a randomly moving result around correct temperature.
Because it’s vcc is supplied from an obniz and results read by an obniz A/D. So, it’s doubled.
When you need to avoid this ripple noise,
- Try other USB adaptor
- add a capacitor around 100uF to J1 on an obniz. (It require soldering. )