Test of the PI connected on the expansion control board

The test done powering the PI with a power supply and the expansion board with a Lipo didn't work:

the i2c scan command:

sudo i2cdetect -y 1

doesn't find any device

Using the same power source (maybe the negative is common this way), the same command find something:

0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f

00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- 1e -- 
20: 20 21 -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- -- 
40: 40 -- -- -- -- -- -- -- 48 -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: 70 -- -- -- -- -- -- --

Let's compare the devices address known, with the scan result now:

Iopiplus bus 1 0x20

Iopiplus bus 2 0x21

ADC ADS1015

0x48 ADR -> GND

0x49 ADR -> VDD

0x4A ADR -> SDA

0x4B ADR -> SCL

PCA9685 multi servo:

Board 0:  Address = 0x40  Offset = binary 00000 (no jumpers required)

Board 1:  Address = 0x41  Offset = binary 00001 (bridge A0 as in the photo above)

Board 2:  Address = 0x42  Offset = binary 00010 (bridge A1)

Board 3:  Address = 0x43  Offset = binary 00011 (bridge A0 & A1)

Board 4:  Address = 0x44  Offset = binary 00100 (bridge A2

Address 0x70 for addressing all PCA9685 devices simultaneously. See section 7.1.2 of the datasheet: http://www.adafruit.com/datasheets/PCA9685.pdf

OLED DISPLAY

address between 0x78 (or 0x7A), selectable with jumpers, or 0x3C

HMC5883L

7-bit address        0x1E

8-bit read address   0x3D

8-bit write address  0x3C