What I2C functions are supported?

Michael_Lowell · November 7, 2023, 12:21am

Hi, I have been reading the Linux Kernel Documentation on I2C programming from user space and it says you’re supposed to check for what functionality is supported by your device using some system calls.

github.com

torvalds/linux/blob/master/include/uapi/linux/i2c.h

/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
/*
 * i2c.h - definitions for the I2C bus interface
 *
 * Copyright (C) 1995-2000 Simon G. Vogl
 * With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi> and
 * Frodo Looijaard <frodol@dds.nl>
 */

#ifndef _UAPI_LINUX_I2C_H
#define _UAPI_LINUX_I2C_H

#include <linux/types.h>

/**
 * struct i2c_msg - an I2C transaction segment beginning with START
 *
 * @addr: Slave address, either 7 or 10 bits. When this is a 10 bit address,
 *   %I2C_M_TEN must be set in @flags and the adapter must support
 *   %I2C_FUNC_10BIT_ADDR.

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I was what functionality is supported by the Le-potatoe I2C adapter? The tutorials/instructions are all a little vague, it really shouldn’t be so hard to program the IC2 adapter and get some communication going.

librecomputer · November 7, 2023, 2:00am

I2C is a standard interface with baud rate and bit modes. They’re fairly standard and consistent across platforms. There’s nothing special unless you get into really corner case scenarios with high speed, specific timing requirements, and other niche applications.

Michael_Lowell · November 7, 2023, 7:33am

So I figured out from a lot of reading I think. What is still not clear on the Libre Board explicitly is how do I change the I2C speed? Default is 100khz? Can I go faster on the libreboard?

Thanks

librecomputer · November 7, 2023, 7:03pm

Yes, you can set the speed using standard Linux facilities.