pxt-calliope/docs/reference/pins/i2c-write-buffer.md

i2c Write Buffer

Write data from buffer to a device at an I2C address.

pins.i2cWriteBuffer(0, null, false);

A device connected to the I2C pins on the @boardname@ at the address is selected to write data to. If the device is ready to take in your data, some or all of the data in your buffer is written to it.

~hint

Simulator

This function needs real hardware to work with. It's not supported in the simulator.

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Parameters

• address: the 7-bit I2C address to read the data from.
• buffer: a buffer that contains the data to write to the device at the I2C address.
• repeated: if true, don't send a stop condition after the write. Otherwise, a stop condition is sent when false (the default).

~ hint

A repeated start condition is set to help make sure that when you want to write data miltiple times from the device at once, it can happen without interruption. A start conditon is sent (if repeated is true) each time a buffer is written without a matching stop condition. When the last buffer is written, the stop conditon can be sent by setting repeated to false. For single writes, don't use repeated or set it to false.

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Example

Tell a device connected to the I2C pins with the address of 141 to respond to a read status command. The device sends the status data on the I2C wires if receives a command byte equal to 0. 32 bytes of status data is read into a buffer.

The third byte is changed and the buffer is sent back to have the device update its status.

const i2cDevice = 141;
pins.i2cWriteNumber(i2cDevice, NumberFormat.UInt8LE, 0)
let i2cBuffer = pins.i2cReadBuffer(i2cDevice, 32, false);
i2cBuffer.setNumber(NumberFormat.UInt8LE, 2, 0)
pins.i2cWriteBuffer(i2cDevice, i2cBuffer, false)

See also

i2c read buffer, buffer

What's I2C?