Part Number: MSP430FR5992
Dear all,
I’m trying to implement an I2C sensor (LIS3DH) into my program for an MSP420FR599x via the eUSCI_B0. Sadly after reading the Family data sheet I’m more confused how to set it up than before – but I’m hopeful you are able to help me. The problem is surely an easy one for someone proficient with the I2C protocol and/or the MSP…. neither am I ;) .
The sensor defines the communication as the following (p.26 DS):
START -- slave-address+write-bit -- wait AK -- send 8bit sub address – wait AK – reapeated START - slave-address+read-bit -- wait AK -- get 8bit data -- no master acknowledge -- STOP
So the MSP needs to send a sub address / command as the first “databyte” and after the AK the MSP should perform a repeated start followed by a read prosses to the slave-address.
I’m at a loss how to initialize the i2c usci for this case and how to perform this transmission with a follow up read out… is it even possible or do I need to do it all “manually” via software?
Currently I initialize the usci via:
UCB0CTLW0 = UCSWRST; // reset state
UCB0CTLW0 |= UCMODE_3 | UCMST | UCSLA10_0 | UCTXSTT; // I2C | master mode | SLADD 7bit | repeated start
UCB0CTLW0 |= UCSSEL_2; //SMCLK
UCB0BRW = 20; //MCLK = 2MHz -> baud rate: MCLK / 20 = 100kHz
UCB0CTLW1 = UCASTP_0; // no STOP assertion
UCB0TBCNT = 1; // 1 bytes of data
UCB0CTLW0 &= ~UCSWRST;
In a read byte function I would set up the slave address (CSA) and if I want to transmit or receive… do I need to set the read/write bit manually with a bitmask into the slave address or does it get added automatically via the UCTR? I would then send the sub address as a transmission and after getting the AK I would start a receiving?!?
Is it the correct way to handle this, or am I missing a functionality which is hardware implemented?
I would really appreciate an small example, the TI examples are a bit too simple or do too much at once.
Best wishes and thank you for your help
Tobias
