I2C - MSP430 to MSP430 problems

[brelliott18 2]

Trying to use I2C to connect 2 X MSP430.

 

Using Wire.write ('H') and 'L ' char to send to Slave via 4K7 pull-ups to turn on / off slave led.

 

 Using Wire.onReceive(receiveEvent) , void receiveEvent ( int howMany )   etc.

 

Have added delays at various places.

 

Have programmed then removed PC connections, use separate PSU

 

ReceiveEvent appears not to work.

 

Have old analogue scope - clock /data signals appear to be ' very dirty ' and ' noisy '

 

Change to 10K pull ups ?  Any suggestions ?  Thanks

[brelliott18 2]

PS I have removed GREEN LED P1.6 link !

[LiviuM 43]

Hi @@brelliott18,

 

There are some known problems with i2c on 2553 Launchpads, mentioned in various posts over this forum.

One of them is mentioned in http://forum.43oh.com/topic/2641-i2c-lcd/page-2#entry75927; in this post is also a link to a solution http://e2e.ti.com/support/development_tools/code_composer_studio/f/81/p/529036/1924562#1924562

 

Have you already seen this posts? Have you tried the solutions presented in them?

 

Regards,

Liviu

[LIJsselstein 9]

If you see noise than that could be ringing caused by fast rise times of the digital I/O. You can try to add a ~50 Ohm resistor in series the SDA and SDL lines, place the resistor close to the transmitter.

[brelliott18 2]

Hi @@brelliott18,

 

There are some known problems with i2c on 2553 Launchpads, mentioned in various posts over this forum.

One of them is mentioned in http://forum.43oh.com/topic/2641-i2c-lcd/page-2#entry75927; in this post is also a link to a solution http://e2e.ti.com/support/development_tools/code_composer_studio/f/81/p/529036/1924562#1924562

 

Have you already seen this posts? Have you tried the solutions presented in them?

 

Regards,

Liviu

 

Thanks for the advice. Have inserted ' Wire.setModule(0) as suggested - This just seems to prevent begin and end transmission loops working altogether. One problem seems to be waveforms coming from SDA / SCL - either not present or very noisy.

[chicken 630]

How long are the wires over which you want to do I2C?

Are the grounds connected?

Weaker (i.e. higher value) pull-ups will make noise issues worse.

[energia 485]

As @@chicken mentioned make sure you have a ground connection between the 2 LaunchPads.

Could you also post the 2 Sketch so that we can have a look at that as well?

[brelliott18 2]

Latest : Have used exactly the same code with ARDUINOs  UNO and NANO instead of 2 X  MSP430 2553  [ used Version 17 of Energia for MSP devices  ].......

..............The code WORKS on these ARDUINO  devices !!!

  [  I simply send 'H' and ' L' chars to turn LED on / off using Wire.begin then Wire.beginTransmission then Wire.endTransmission plus delays for MASTER .

For SLAVE ( another MSP430 2553 ) I use  Wire.onReceive( receiveEvent) then VOID receiveEvent ( int howMany) then ' while Wire.available  and Wire.Read '  etc. ]

Use 4K7 pull ups on p1.7 , P1.6 plus   Common Ground.

I assume, perhaps, that  the Registers are not being Set up properly ? - Have also noticed that there are NO examples on YouTube as opposed to the ARDUINO.

Has anyone ever managed to connect 2 MSP430 via I2C , I wonder ?

 

 

 

 

 

 

 

 

 

 

[Rei Vilo 695]

@brelliott18

Have you gone through the reference at http://energia.nu/reference/wire/?

[brelliott18 2]

Thanks for the reply

Yes, I have. The point is that identical code on the Arduinos works but not on MSP430s

 

So either the delays need changing ?  - I'm using 3 seconds on the MASTER between begin and end transmissions and about 0.5 second on the SLAVE - I have changed these but it doesn't seem to a make any difference.

 OR  :  Perhaps  the Registers are  not being set up correctly but that's a pure guess.

 

PS I can't the C language - I'd like to do everything in Forth in possible.

[LiviuM 43]

In the post I've linked above the solution was to replace the twi.c & twi_sw.c with new ones, found in the e2e forum. Have you also replaced them?

[brelliott18 2]

Not yet - will give it a try - THANKS !!!

[brelliott18 2]

Replaced files  - Makes no difference.

Ran your program to return addresses of serial devices - after removing ' Wire.setModule(0) ' line which crashes it.

The program returned a continuous stream of addresses from 0 to 127 -  Is this a sign that the MSP430 itself cannot act as slave because it doesn't recognise any addresses ( not even ' 0 ' ) , perhaps   ?

 

Regards

[B@tto 51]

Hi,

Last year I add a lot of troubles with i2c in Energia. I solved them but I don't know if Energia team included my corrections : 

 

[brelliott18 2]

It appears the latest twi.c file from GITHUB  does NOT appear to  incorporate B@TTO modifications:- 

 

This is my understanding of the mods required noted by  //********************

 

Is this correct ? 

 

[ If so , it would seem a good idea for ENERGIA to update this file, surely ?? - How does one get this to happen ? ]

 

[ The other code needed is  to insert Wire.setModule(0)  before Wire.begin ,   so I'm told ]

 

 

****************LATEST  TWI.C   [  FROM LINE 839 ] ****************************

 

/* Slave transmit mode (twi_state = TWI_STX) */

 }

else {                  // ***** REPLACE WITH  else if  ( twi_state == TWI_STX ) {

 // copy data to output register

 UCBxTXBUF = twi_txBuffer[twi_txBufferIndex++];

 // if there is more to send, ack, otherwise nack

if(twi_txBufferIndex < twi_txBufferLength){

 } else {

UCBxCTL1 |= UCTXNACK; // Generate NACK condition }

 

}

// ************************PLUS ****************

} else {
	if (twi_sendStop) {
	/* All done. Generate STOP condition and IDLE */
	UCBxCTL1 |= UCTXSTP; // *********************  ADD UCxIFG &=  ~ UCB0TXIFG ;