RE: how to get a repeated start on I2C

weightwatcherphil — Thu, 27 Jul 2023 02:53:12 GMT

hi vidar,

the above code did not work. but the function

i2c_write_read_dt

got me what i needed

static inline int i2c_write_read(const struct device *dev, uint16_t addr,

const void *write_buf, size_t num_write,

void *read_buf, size_t num_read)

{

struct i2c_msg msg[2];

msg[0].buf = (uint8_t *)write_buf;

msg[0].len = num_write;

msg[0].flags = I2C_MSG_WRITE;

msg[1].buf = (uint8_t *)read_buf;

msg[1].len = num_read;

msg[1].flags = I2C_MSG_RESTART | I2C_MSG_READ | I2C_MSG_STOP;

return i2c_transfer(dev, msg, 2, addr);

}

i get a write , with a repeated start followed by a read and then a stop.

you may close this ticket

Vidar Berg — Tue, 25 Jul 2023 12:00:58 GMT

Hi phil,

The i2c_transfer() function is blocking, so the transaction will be complete upon return. The APIs that are non-blocking are documented as asynchronous in the API documentation here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/hardware/peripherals/i2c.html

Best regards,

Vidar