I2C Sensor Addressing

I2C uses a 7-bit addressing scheme (there is also 10-bit addressing but we are not using it). When sending an address over the bus, the address is shifted to the left 1 bit and the least significant bit is used to indicate read or write. It is important to know this because LEGO and 3rd-party sensor manufacturers use the shifted value as the address in their documentation. This shifted value is also used in most other NXT/EV3 programming languages/environments.

IMPORTANT NOTE: I2C addresses 0x01 through 0x07 (unshifted) are reserved for special use by the I2C specifications. However, these addresses are used by some sensors anyway (most notably the NXT Ultrasonic sensor). The ev3dev kernel has been patched to make these work, but many userspace tools (like i2c-tools) will not work with devices at these addresses.

ev3dev is different because the Linux kernel uses the unshifted value as the I2C address. This means you will have to convert the value to get the correct address. Shift to the right is the same as divide by 2, so get out your hexadecimal calculator and do some math!

Or for the engineer type folks that prefer tables...

Shifted Address (write/read)	Unshifted Address	Notes	Shifted Address (write/read)	Unshifted Address	Notes
0x00/0x01	0x00	I2C spec: General call address / START byte	0x80/0x81	0x40
0x02/0x03	0x01	NXT Ultrasonic and many 3rd party sensors I2C spec: CBUS address	0x82/0x83	0x41
0x04/0x05	0x02	LEGO Energy Storage I2C spec: Reserved for different bus format	0x84/0x85	0x42
0x06/0x07	0x03	I2C spec: Reserved for future purposes	0x86/0x87	0x43
0x08/0x09	0x04	I2C spec: Hs-mode master code	0x88/0x89	0x44
0x0A/0x0B	0x05	I2C spec: Hs-mode master code	0x8A/0x8B	0x45
0x0C/0x0D	0x06	I2C spec: Hs-mode master code	0x8C/0x8D	0x46
0x0E/0x0F	0x07	I2C spec: Hs-mode master code	0x8E/0x8F	0x47
0x10E/0x11	0x08	Some HiTechnic sensors	0x90/0x91	0x48
0x12/0x13	0x09		0x92/0x93	0x49
0x14/0x15	0x0A	mindsensors.com Light Sensor Array	0x94/0x95	0x4A
0x16/0x17	0x0B		0x96/0x97	0x4B
0x18/0x19	0x0C		0x98/0x99	0x4C	LEGO Temperature Sensor
0x1A/0x1B	0x0D		0x9A/0x9B	0x4D
0x1C/0x1D	0x0E		0x9C/0x9D	0x4E
0x1E/0x1F	0x0F		0x9E/0x0F	0x4F
0x20/0x21	0x10		0xA0/0xA1	0x50
0x22/0x23	0x11		0xA2/0xA3	0x51
0x24/0x25	0x12		0xA4/0xA5	0x52
0x26/0x27	0x13		0xA6/0xA7	0x53
0x28/0x29	0x14		0xA8/0xA9	0x54
0x2A/0x2B	0x15		0xAA/0xAB	0x55
0x2C/0x2D	0x16		0xAC/0xAD	0x56
0x2E/0x2F	0x17		0xAE/0xAF	0x57
0x30/0x31	0x18		0xB0/0xB1	0x58
0x32/0x33	0x19		0xB2/0xB3	0x59
0x34/0x35	0x1A		0xB4/0xB5	0x5A
0x36/0x37	0x1B		0xB6/0xB7	0x5B
0x38/0x39	0x1C		0xB8/0xB9	0x5C
0x3A/0x3B	0x1D		0xBA/0xBB	0x5D
0x3C/0x3D	0x1E		0xBC/0xBD	0x5E
0x3E/0x3F	0x1F		0xBE/0xBF	0x5F
0x40/0x41	0x20		0xC0/0xC1	0x60
0x42/0x43	0x21		0xC2/0xC3	0x61
0x44/0x45	0x22		0xC4/0xC5	0x62
0x46/0x47	0x23		0xC6/0xC7	0x63
0x48/0x49	0x24		0xC8/0xC9	0x64
0x4A/0x4B	0x25		0xCA/0xCB	0x65
0x4C/0x4D	0x26		0xCC/0xCD	0x66
0x4E/0x4F	0x27		0xCE/0xCF	0x67
0x50/0x51	0x28		0xD0/0xD1	0x68
0x52/0x53	0x29		0xD2/0xD3	0x69
0x54/0x55	0x2A		0xD4/0xD5	0x6A
0x56/0x57	0x2B		0xD6/0xD7	0x6B
0x58/0x59	0x2C		0xD8/0xD9	0x6C
0x5A/0x5B	0x2D		0xDA/0xDA	0x6D
0x5C/0x5D	0x2E		0xDC/0xDD	0x6E
0x5E/0x5F	0x2F		0xDE/0xDF	0x6F
0x60/0x61	0x30		0xE0/0xE1	0x70
0x62/0x63	0x31		0xE2/0xE3	0x71
0x64/0x65	0x32		0xE4/0xE5	0x72
0x66/0x67	0x33		0xE6/0xE7	0x73
0x68/0x69	0x34		0xE8/0xE9	0x74
0x6A/0x6B	0x35		0xEA/0xEB	0x75
0x6C/0x6D	0x36		0xEC/0xED	0x76
0x6E/0x6F	0x37		0xEE/0xEF	0x77
0x70/0x71	0x38		0xF0/0xF1	0x78	I2C spec: 10-bit slave addressing
0x72/0x73	0x39		0xF2/0xF3	0x79	I2C spec: 10-bit slave addressing
0x74/0x75	0x3A		0xF4/0xF5	0x7A	I2C spec: 10-bit slave addressing
0x76/0x77	0x3B		0xF6/0xF7	0x7B	I2C spec: 10-bit slave addressing
0x78/0x79	0x3C		0xF8/0xF9	0x7C	I2C spec: Reserved for future purposes
0x7A/0x7B	0x3D		0xFA/0xFB	0x7D	I2C spec: Reserved for future purposes
0x7C/0x7D	0x3E		0xFC/0xFD	0x7E	I2C spec: Reserved for future purposes
0x7E/0x7F	0x3F		0xFE/0xFF	0x7F	I2C spec: Reserved for future purposes