I2C Arbitration Lost errors

[mspenard603]

Hi All,

 I have my RT1062 setup to be a I2C master. I send out a Read command as seen below, and very often but not always, my master's ISR kicks out an Arbitration Lost error (kStatus_LPI2C_AribitrationLost). Right after it sends the Read Bit, and control is to be handed off to the slave to put the Read Data on SDA. 

Any insight as to what is going on here? Do I have a pin config issue? Or is there a timing issue in the driver in handing things off?

[Hui_Ma]

Hi,

I would recommend customer to refer MCUXpresso SDK for MIMXRT1060-EVK board  I2C demo.

The demo located with below path:

..\SDK_2.5.0_EVK-MIMXRT1060\boards\evkmimxrt1060\driver_examples\lpi2c

And please check below I2C circuit, please add external pull up resistors with I2C_SDA, I2C_SCL pins:

Have a great day,
Mike

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[mspenard603]

Traced it down to a timing issue... Despite both master (RT1602) and slave (Cypress PSOC3) being set for 100kbps the slave needed to be overclocked slightly.

The slaves duty cycle between SDA bits must of been, from time to time, just longer than the masters clock pulse width. Putting master into an Arbitration Lost condition and letting go of SCL altogether.

Interesting that it was doing this only on the first byte of a Read command. PSOC I2C code handles that byte different of course, so it can unpack the address.That extra bit of work must of put the SDA pulse cycle just under 100khz from time to time.

[Hui_Ma]

Hi,

I check Cypress PSOC3 datasheet with below description:

And it suggested to use 4.7Kohm pull up with I2C Normal mode:

Please check if the hardware circuit change could make the I2C read working.

best regards,

Mike

[mspenard603]

I was running 4.7k earlier. Then tried 2.7k. Still had the Arbitration Loss issue after Read-command. Only solution was to over-clock the PSOC3 slave end. It's at an effective rate of 125kbps.

[Hui_Ma]

Thanks for the info.

best regards,

Mike