Please provide a simple a working and simple example of the new I2C API (IDFGH-14090)

[juantxorena]

Answers checklist.

• I have read the documentation ESP-IDF Programming Guide and the issue is not addressed there.
• I have updated my IDF branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

General issue report

Since version v5.2 there's a new API for I2C devices, and the old one is deprecated. There's only an example in the repo, but it's IMHO overly complicated and not very applicable to a lot of people.

See the old example:
https://github.com/espressif/esp-idf/tree/release/v5.1/examples/peripherals/i2c/i2c_simple

It is a simple device where it's configured, and it's shown how to read from a register and write to a register. Very few lines of code, and enough to get a gist of the API.

And now compare this to the new example, for reading and writing from an EEPROM:
https://github.com/espressif/esp-idf/tree/master/examples/peripherals/i2c/i2c_eeprom

it's a mess with a ton of type definitions, apparently for no reason:

esp-idf/examples/peripherals/i2c/i2c_eeprom/components/i2c_eeprom/i2c_eeprom.h

Line 27 in 7a305c0

typedef struct i2c_eeprom_t i2c_eeprom_t;

memory allocations where in the old one none was needed:

esp-idf/examples/peripherals/i2c/i2c_eeprom/components/i2c_eeprom/i2c_eeprom.c

Lines 28 to 40 in 7a305c0

	out_handle = (i2c_eeprom_handle_t)calloc(1, sizeof(*out_handle));
	ESP_GOTO_ON_FALSE(out_handle, ESP_ERR_NO_MEM, err, TAG, "no memory for i2c eeprom device");
	i2c_device_config_t i2c_dev_conf = {
	.scl_speed_hz = eeprom_config->eeprom_device.scl_speed_hz,
	.device_address = eeprom_config->eeprom_device.device_address,
	};
	if (out_handle->i2c_dev == NULL) {
	ESP_GOTO_ON_ERROR(i2c_master_bus_add_device(bus_handle, &i2c_dev_conf, &out_handle->i2c_dev), err, TAG, "i2c new bus failed");
	}
	out_handle->buffer = (uint8_t*)calloc(1, eeprom_config->addr_wordlen + I2C_EEPROM_MAX_TRANS_UNIT);

managing a buffer manually:

esp-idf/examples/peripherals/i2c/i2c_eeprom/main/i2c_eeprom_main.c

Lines 56 to 60 in 7a305c0

	uint8_t buf[LENGTH];
	for (int i = 0; i < LENGTH; i++) {
	buf[i] = i;
	}
	uint8_t read_buf[LENGTH];

etc. It just looks overly verbose and complicated.

So please provide a simple example for the new I2C API where it's shown how to:

• Configure the master and the device
• Read from a register
• Write to a register

[suda-morris]

This example function should illustrate the "i2c write to a register" well: https://github.com/espressif/esp-idf/blob/master/examples/peripherals/i2c/i2c_tools/main/cmd_i2ctools.c#L206

This example function should illustrate the "i2c read from a register" well: https://github.com/espressif/esp-idf/blob/master/examples/peripherals/i2c/i2c_tools/main/cmd_i2ctools.c#L152

[suda-morris]

linked in #14315