Firmware-75 Message-010

I2C DATA (10, 0Ah)

In host mode the USB–microDig sends digital (I2C) sensor values, after being activated through a FUNCTION command, in the I2C DATA message.

The [BODY] of the I2C DATA message contains a list of sensor values as specified in the function’s method. 8-bit values are sent as two nibbles inside a byte each:

00000yyy:	yyy = [0..7]; sensor input number, where the first input number = 0 and the last (8th) input number = 7
0ddddddd:	ddddddd = [0-127]; I2C device address
0nnnnnnn:	nnnnnnn = [0-127]; function number
0ppppppp:	ppppppp = [0-127]; function method or parameter
0000dddd:
0000eeee:	ddddeeee = [0..255]; data (number of bytes as per function specification)

Example:

The USB-microDig has function Orient3D, method 1, enabled an Orient3D sensor with device address 96 connected to I2C port 1. The USB-microDig acquires the value 90 (heading east), 45 (pitch down), and -45 (roll to the right). The USB-microDig sends the following message in host mode:

240, 125, 0 {DEV}, 10 {I2C DATA}, 0 {I2C port}, 96 (address of device}, 125 {Orient3D}, 1 {heading/pitch/roll}, 0 {dddd of heading 1st byte }, 10 {eeee of heading 1st byte}, 8 {dddd of heading 2nd byte}, 12 {eeee of heading 2nd byte}, 2 {dddd of pitch}, 0 {eeee of pitch}, 13 {dddd of roll}, 15 {eeee of roll}, 247 (F0h, 7Dh, 00h, 0Ah, 00h, 64h, 7Dh, 01h, 00h, 0Ah, 08h, 0Ch, 02h, 00h, 0Dh, 0Fh, F7h)

The heading value from the Orient3D is ( 0 * 16 (ie. 4-bit shift) + 10 ) * 256 (ie. 8-bit shift) + 8 * 16 (i.e. 4-bit shift) + 12 = 2700, corresponding to 270.0 degrees.

The pitch value from the Orient3D is 2 * 16 (i.e. 4-bit shift) + 0 = 32 unsigned, so that the two’s complement signed value is also 32, corresponding to 32 * 359 / 255 = 45 degrees.

The roll value from the Orient3D is 13 * 16 (i.e. 4-bit shift) + 15 = 223 unsigned, so that the two’s complement signed value is 223 – 256 = -32. Corresponding to -32 * 359 / 255 = -45 degrees.