I2C Entity

API Documentation: [cpp] [python] [.NET] [LabVIEW]

BrainStem modules may have the ability to read, write data on up to 2 I2C bus’s

Read

i2c [ index ] . read => (unsigned char) address, (unsigned char) length <= (unsigned char*) data

Reads up to 26 bytes from the i2c bus given by the index. The parameters are the I2C address of the device on the bus, and the number of bytes to read. The result is the data that was read or an error.

Write

i2c [ index ] . write => (unsigned char) address, (unsigned char) length, (unsigned char*) data <= (unsigned char) result

Writes up to 26 bytes to the i2c bus given by the index. The parameters are the I2C address of the device on the bus, the number of bytes to write, and the data to write. The result is the result error condition or none.

Set Pullup

i2c [ index ] . setPullup => (unsigned char) bool

Sets software controlled pullup state on modules which have software controllable pullups. This setting is saved when a call to system.save is made so that Pullup settings on bus 0 can persist.

Speed (Get/Set)

i2c [ index ] . getSpeed <= (unsigned char) speed
i2c [ index ] . setSpeed => (unsigned char) speed

Returns or sets the I2C bus communication speed. The speed setting controls the clock frequency for I2C transactions on the specified bus.

I2C Speed Options

Value	Name	Description
0	Default	Default I2C speed (typically 100 kHz)
1	100Khz	Standard I2C speed (100 kHz)
2	400Khz	Fast I2C speed (400 kHz)
3	1000Khz	Fast Plus I2C speed (1 MHz)

Code Examples

C++

// All commands return aErr values when errors are encountered and aErrNone on
// success.
char buff[2];
stem.i2c[0].read(0x42, 0x02, buff); // reads two from device with address 0x42.
char wrbuff[] = {0xBE, 0xEF};
stem.i2c[0].write(0x42, 0x02, wrbuff); // writes 0xBEEF to the device with address 0x42
stem.i2c[0].setPullup(true); //enables pullup on bus 0
stem.i2c[0].setSpeed(1); // sets I2C speed to 100 kHz (i2cSpeed_100Khz)
stem.i2c[0].setSpeed(2); // sets I2C speed to 400 kHz (i2cSpeed_400Khz)
stem.i2c[0].setSpeed(3); // sets I2C speed to 1 MHz (i2cSpeed_1000Khz)
unsigned char speed;
stem.i2c[0].getSpeed(&speed); // gets current I2C speed

Reflex

Currently this entity is not available from within the reflex language.

Python

The length parameter for I2C write is not used in python.

result = stem.i2c[0].read(0x42, 0x02) # reads two bytes from the i2c bus. The value is given in result.value
print result.value
err = stem.i2c[0].write(0x42, b'\xbe\xef') #  writes b'\xbe\xef' to the i2c bus.
print err
err = stem.i2c[0].setPullup(True)
print err
err = stem.i2c[0].setSpeed(1) # sets I2C speed to 100 kHz (i2cSpeed_100Khz)
print err
speed = stem.i2c[0].getSpeed() # gets current I2C speed
print speed.value