i2c communication problems

[billt79]

Hi,

I have been having a lot of problems communicating with an Atmel SAM D09 as a slave, and an nrf51422 as a master.

I seem to have two problems, hopefully solving just one will get me where I need to be. but I can't seem to narrow it down. The first issue, I have been trying to use a slightly modified twi_sw_master.c to communicate with the slave, this has worked with plenty of other i2c devices out there, like EEPROMs Acelerometers, and PMICs however the Atmel won't ack. The reason I believe this to be a problem, is it doesn't run at exactly 100Khz (best i can get is 94Khz), this seems highly unlikely to me, but it is the only thing that is apparent as the Atmel is returning no error while polling the interrupt flags, and all the config is set as required. It is also pulling up both of its i2c pins, which would indicate that it is working. I have done plenty of debugging with uart, and all seems normal.

To get around this i have tried using twi_hw_master.c to work, and i do get 100Khz exactly, however the waveform i see on my scope looks wrong. To my understanding, there are 9 clock pulses on SCL, the last one being for an ack/nack, this was present on the sw version, but on the hw version it is not present and there also does not appear to be a valid stop condition, although no data is being transferred due to the lack of an ack. My aim is to use the self programming function of the Atmel SAM to update it OTA via the BLE on the nrf. the code on the Atmel is from the ASF, so i can be quite sure it works. Also worth noting that the Atmel chip is configured to respond to any address between 0-127 regardless. Unfortunately for me i am very restricted on GPIOs on the nrf, so using something else is out of the question.

[RK]

Clicking that link takes me still to a 180x100 image, the title on the page is actually "scope.png (180x100)"! It's not clickable either, not that I can see, so there's no full-sized one I can see. Not that I suspect it would help much.

I'm pretty sure the tw_hw_master works fine, it's even simpler than the sw one. I don't use it myself, I write the registers directly but it's the same thing in the end. The TWI hardware I've never had a problem with on the nrf51.

The only example I see for the D20 is the D20 bootloader, shame there isn't a simpler I2C slave test, the unit tests only test master mode so they don't help. I can only suggest setting up the simplest I2C project you can, perhaps one of the other SAM boards has a version you can modify although I don't see much.