MSP432 I2C_masterSendMultiByteStart sends first byte only once

Jonathan Morr

Hi!

I am right now writing a driver for an I2C LCD Display.

void LCD_sendCMD(uint8_t cmd)
{
	while (MAP_I2C_masterIsStopSent(EUSCI_B0_MODULE) == EUSCI_B_I2C_SENDING_STOP); 
	I2C_masterSendMultiByteStart(EUSCI_B0_MODULE, CBCMD);
	I2C_masterSendMultiByteFinish(EUSCI_B0_MODULE, cmd);
}

The Display needs a controlbyte which determines if the following data is a command or data. I use the driverlib function I2C_masterSendMultiByteStart which starts the communication and sends the first byte, in this case the controlbyte for a command (CBCMD = 0x00).

I've seen on the oscilloscope that this controlbyte gets only sent the first time i call this function. The next time i call I2C_masterSendMultiByteStart it just sends the I2C address and proceeds in the code with sending the actual command via I2C_masterSendMultiByteFinish, making it incomplete. Am i missing something here? Do I have to clear any Interruptflags or reset something so the function starts over from the beginning?

I didn't find anything regarding this in the documentation.

I am using CCS 6.1.1.00022 with an MSP-EXP432P401R rev 1.0

Jonathan

over 8 years ago

0 DavidL over 8 years ago

TI__Mastermind 25045 points

Hi Jonathan,

Please take a look at the writeI2C function in this thread:

e2e.ti.com/.../1701554

Hopefully it will help you correct this problem.

Regards,

David

0 DavidL over 8 years ago in reply to DavidL

TI__Mastermind 25045 points

I'm marking the thread closed due to inactivity, but you can always use "reject answer" or simply post back to re-open it if you need more help on this issue.

0 robert schaefer over 7 years ago in reply to DavidL

Expert 2040 points

Hi,

I just ran into the same problem.

I am going to try the driver you posted, and reply on whether it works or not.

bob s.

0 robert schaefer over 7 years ago in reply to robert schaefer

Expert 2040 points

Argh. I'm going to have to modify your driver somewhat, I've got a bespoke 432 that uses EUSCI_B2_BASE, your driver uses EUSCI_B1_BASE.

0 robert schaefer over 7 years ago in reply to robert schaefer

Expert 2040 points

One more problem with the updated driver as is, the read returns early because it checks the busy flag, which gets unbusy between bytes on a multibyte transfer.

0 robert schaefer over 7 years ago in reply to robert schaefer

Expert 2040 points

The read terminates early hanging on status indicating that read interrupts have stopped before all (decrementing count of) data has been read.
Why do you pair multibyte reads in your interrupt handler and throw away one byte?

*pData++ = MAP_I2C_masterReceiveMultiByteNext(EUSCI_B1_MODULE);
ui8DummyRead= MAP_I2C_masterReceiveMultiByteNext(EUSCI_B1_MODULE);

0 robert schaefer over 7 years ago in reply to robert schaefer

Expert 2040 points

I'm guessing the dummy read is the ack, as shown by the bus pirate direct reads.
Ok, my conclusion on your driver, per what bus pirate shows, is your driver can't read because it doesn't do a proper handshake.
This is what bus pirate shows:
[0xD2+0x00+[0xD3+0x00+0x00+]

This is, I think, what it should be: [0xD2+0x00+0xD3+0x00+0x00+]

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MSP432 I2C_masterSendMultiByteStart sends first byte only once