2.3 I²C Communication

Similar to the UART mode, the MSP-BSL supports the I²C protocol, starting with firmware version 2.1. All data sent to the virtual COM port is output on the SDA and SCL pins (see Section 4.2). Data received from I²C is forwarded to the PC. The MSP-BSL acts as a transparent USB-to-I²C bridge, except that it returns an error code (055h) to the PC if the I²C communication fails. The MSP-BSL has a state machine that emulates this transparent behavior.

The MSP-BSL operates as an I²C master and uses 7-bit addressing mode. The slave address for the MSP430 or MSP432P4xx target is 048h, and the slave address for the MSP432E4 target is 042h.

To start I²C BSL communication, perform the following steps, depending on the device family.

For the MSP430 family:

1. The host triggers the MSP-BSL Rocket with 100001 or 400001 bit rate.
2. The slave address generated by MSP-BSL Rocket is 0x48.
3. For custom I²C address only : The host triggers the MSP-BSL Rocket with (100000 + slaveAddress) or (400000 + slaveAddress).
4. The host starts the programming with 100000 or 400000 standard bit rate.

For the MSP432P4xx family:

1. The slave address generated by MSP-BSL Rocket is 0x48.
2. For custom I²C address only : The host triggers the MSP-BSL Rocket with (100000 + slaveAddress) or (400000 + slaveAddress).
3. The host starts the programming with 100000 or 400000 standard bit rate.

For the MSP432E4 family:

1. The host triggers the MSP-BSL Rocket with 100008 or 400008 bit rate.
2. The slave address generated by MSP-BSL Rocket is 0x48.
3. For custom I²C address only : The host triggers the MSP-BSL Rocket with (100000 + slaveAddress) or (400000 + slaveAddress).
4. The host starts the programming with 100000 or 400000 standard bit rate.

The MSP-BSL supports I²C Standard Mode (Sm) with a maximum transfer rate of 100 kbps and I²C Fast Mode (Fm) with a maximum transfer rate of 400 kbps. Both of these modes are selected by changing the bit rate of the serial connection from the PC to the MSP-BSL.