AM3358: Regarding Configuring am335x I2C1 Bus as I2C Slave and Communication with SMBUS Master

JINS PAUL

Part Number: AM3358

I am currently working on a project that requires configuring the am335x I2C1 bus as an I2C slave (SMBUS slave) and establishing communication with an SMBUS master. However, after exploring the TI am335x Linux SDK, I discovered that it primarily supports master mode for the I2C interface. As I am new to Linux driver development, I am seeking guidance on where to begin or any helpful resources you might recommend.

https://github.com/enndubyu/omap_i2c_slave do you have any information regarding this code change?

Additionally, I have a question regarding the configuration of the I2C slave address in the device tree. Typically, in the device tree, we specify the slave device's address. However, in this scenario, the am335x itself functions as a slave. How would I configure the slave addressing in the Linux environment?

I would greatly appreciate any insights or pointers you could provide to assist me in navigating this process.

Thank you in advance for your time and assistance.

Warm regards,
Paul Jins

over 1 year ago

0 Nick Saulnier over 1 year ago

TI__Guru** 103550 points

Hello Paul,

We do not support I2C slave mode on the TI Linux I2C drivers. For more information, reference

https://e2e.ti.com/support/processors/f/791/t/887456

Regards,

Nick

0 JINS PAUL over 1 year ago in reply to Nick Saulnier

Prodigy 70 points

I've gone through all those e2e TI threads before submitting this support ticket, and I'm wondering why TI hasn't released an I2C slave driver. At the same time, I'm concerned whether modifying the I2C-OMAP (master) driver to support the slave driver at github.com/.../omap_i2c_slave with this patch might affect the master mode. For my setup, I'm using i2c0 and i2c2 buses as masters and i2c1 as a slave.

Is it possible to create my own I2C slave driver for the AM335x? What are all the points that need to be considered?

0 Nick Saulnier over 1 year ago in reply to JINS PAUL

TI__Guru** 103550 points

Hello Paul,

Disclaimer
Before I continue with the response, please note that I can only answer questions about TI software or TI hardware on the forums - I won't be able to answer specific questions about modifying a TI driver, or writing your own driver.

What to keep in mind if you were to try to develop your own I2C slave driver?

First, note that Linux has some limitations around guaranteeing that something will happen within a specific amount of time - even RT Linux is NOT a true real-time operating system. That could cause issues in getting the I2C slave device to respond 100% of the time within a deterministic timeframe. For more information, see https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1024619/am6412-i2c-multi-master-mode/3793533#3793533

Second, note that SMBus block reads are not supported on AM335x. Off the top of my head I wouldn't expect that to impact I2C slave, but I just wanted to make sure you were aware of that limitation as well:

https://e2e.ti.com/support/processors/f/791/p/772463/2880237

https://e2e.ti.com/support/processors/f/791/p/646234/2374308#2374308

Note that the AM335x RTOS SDK does have an I2C slave driver. You may be able to reference that as well. Just keep in mind that we can no longer offer support on the AM335x RTOS SDK:
https://software-dl.ti.com/processor-sdk-rtos/esd/docs/06_03_00_106/AM335X/rtos/index_device_drv.html#i2c

Regards,

Nick

0 JINS PAUL over 1 year ago in reply to Nick Saulnier

Prodigy 70 points

Thank you, Nick.

I have successfully applied the patch from github.com/.../omap_i2c_slave to configure the I2C1 bus as a slave. I tested it by simulating an EEPROM slave driver and was able to read data via the I2C2 master on the same SoC. I realize this is just the beginning of a more extensive journey.

Moving forward, my plan is to continue working on the same driver and develop a new backend driver. This backend driver will have predefined responses to master requests, and my goal is to allow the backend driver itself to handle these requests, instead of relying on the application. The backend driver will have provision for modification of predefined responses, providing flexibility. I intend to isolate this module from others and activate it only when I need to test this specific functionality independently.

Can you please close this ticket as well? https://e2e.ti.com/support/processors-group/processors/f/processors-forum/444259/pwm-ecap-in-capture-mode-for-am335x----how-to-get-value-to-sysfs-to-userspace-from-kernel-driver

I am able to use am335x ECAP module after using AM62X ecap driver.

0 Nick Saulnier over 1 year ago in reply to JINS PAUL

TI__Guru** 103550 points

Hello Paul,

Glad to hear! Good luck in your I2C journey.

Thanks for letting us know that you were able to get the ECAP working the way you needed it as well. It's always helpful for us and future readers to hear how a poster was able to resolve their question. I've added your update to that post for future readers: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1279144/am3358-pwm-ecap-in-capture-mode-for-am335x----how-to-get-value-to-sysfs-to-userspace-from-kernel-driver

Regards,

Nick

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AM3358: Regarding Configuring am335x I2C1 Bus as I2C Slave and Communication with SMBUS Master