How To Access I2C

This guide is about how to access i2c on Android.

Preconditions

  • Android V210128 or newer

Connections

I2C 3
Sensor SCL <-> I2C0_SCK (PIN 22)
Sensor SDA <-> I2C0_SDA (PIN 23)
Sensor GND <-> GND
Sensor VCC <-> 5V or 3.3V //depends on your sensor

I2C 4
Sensor SCL <-> I2C1_SCK (PIN 25)
Sensor SDA <-> I2C1_SDA (PIN 26)
Sensor GND <-> GND
Sensor VCC <-> 5V or 3.3V //depends on your sensor

Detect the device

Detect device on I2C 3:

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# i2cdetect -y -r 3
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

Detect device on I2C 4:

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# i2cdetect -y -r 4
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- UU -- 
10: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- -- 
20: UU -- 22 -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- UU -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- UU -- -- -- 
70: -- -- -- -- -- -- -- --

If you have the right connection you will see the device address, e.g: 0x1e,0x18 and 0x51.

Note

Root privileges required.

Read register from device

Read register 0x0d of device 0x22 on I2C4.

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# i2cget -f -y 4 0x22 0x0d
0x0f

Show device register value

Show register value of device 0x22 on I2C4.

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# i2cdump -f -y 4 0x22 
No size specified (using byte-data access)
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
00: 00 91 07 45 31 60 08 00 22 07 74 0f 00 0f a2 fe    .??E1`?."?t?.???
10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
30: 00 00 00 00 00 00 00 00 00 00 00 00 0c 00 00 00    ............?...
40: 81 28 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ?(..............
50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
e0: 00 00 00 00 00 00 00 00 00 90 39 0c 00 00 00 00    .........?9?....
f0: 00 00 08 00 00 00 00 00 00 00 00 00 00 00 01 00    ..?...........?.

Write device register value

Write 0x20 address register value to 0 of device 0x18 on I2C4,use i2cdump to query

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# i2cset -f -y 4 0x18 0x20 0

#  i2cdump -f -y 4 0x18
No size specified (using byte-data access)
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
00: ff ff ff ff ff ff 00 00 00 00 00 00 00 00 00 00    ................
10: 00 00 00 01 00 03 00 00 00 00 00 00 00 00 00 00    ...?.?..........
20: 00 00 01 01 01 01 01 00 00 01 00 00 01 00 00 00    ..?????..?..?...
30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00    ................
40: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
50: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
60: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
70: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
80: ff ff ff ff ff ff 00 ff ff ff ff ff ff ff ff ff    ................
90: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
a0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
Note

i
Root privileges required.

Access i2c by khadasapi

In addition to the command to access I2C, you can also access through APK. We encapsulate a jar package, which contains the I2C read-write interface,for example
I2C read
Function：public int i2c_read_byte_data(int bus, int addr, int reg)
Parameter：bus: Device mounted I2C bus addr: Device I2C address reg: Device register
Return：Returns the read register value
example：

int Value = getKhadasApi().i2c_read_byte_data(4, 0x0e, 0x60);

I2C write
Function：public int i2c_write_byte_data(int bus, int addr, int reg, int value)
Parameter：bus: Device mounted I2C bus addr: Device I2C address reg: Device register value: Value to set
Return：-1: NG 0: OK
example：

int propertiesValue = getKhadasApi().i2c_write_byte_data(4,0x0e, 0x60, 96);

khadas_api_demo code download

  • git clone https://github.com/khadas/khadas_api_demo -b vim3
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