how to get a repeated start using zephyr I2c functions.

RE: how to get a repeated start using zephyr I2c functions.

weightwatcherphil — Thu, 20 Jul 2023 19:39:06 GMT

I am going to try an use the nrfx_twim_xfer function so you can close this ticket.

thanks

phil

RE: how to get a repeated start using zephyr I2c functions.

Raoul — Thu, 20 Jul 2023 17:04:53 GMT

Hi,

Yep, I see from your newest ticket that you have started work on implementing the nrfx_twim driver.

I don't have experience with using that, I see that this case RE: Continuous Background I2C process mentions NRFX_TWIM_FLAG_REPEATED_XFER in the context of repeated starts.

I hope that gets you further.

Best regards,

Raoul

RE: how to get a repeated start using zephyr I2c functions.

weightwatcherphil — Thu, 20 Jul 2023 15:21:38 GMT

i have found that the I2 driver is really using the TWIM hardware and so now I am looking into how to use the

nrfx_twim_xfer

function which as near as I can tell supports the repeated start option.

I will let you know how it turns out. it will take me a day or two to implement it.

if you think it will not work let me know.

thanks

phil

RE: how to get a repeated start using zephyr I2c functions.

Raoul — Thu, 20 Jul 2023 14:28:31 GMT

Hi Philip,

Try setting the I2C_MSG_RESTART flag for the Zephyr I2C driver. The Zephyr docs warn that "Not all I2C drivers have or require explicit support for this feature", but according to this line, the nrfx driver seems to take it into account.

You could try performing an i2c_write_read() with your sensor, with that flag set.

If you're new to using I2C through Zephyr, please check out this answer by my colleague: How to use I2C on the nRF5340 DK ?

Best regards,

Raoul

RE: how to get a repeated start using zephyr I2c functions.

weightwatcherphil — Mon, 17 Jul 2023 22:19:08 GMT

attached is the actual I2C bus protocol i need.

devzone.nordicsemi.com/.../LC709_5F00_I2c_5F00_bus_5F00_protocol.docx

thanks for your help.

RE: how to get a repeated start using zephyr I2c functions.

weightwatcherphil — Mon, 17 Jul 2023 22:01:22 GMT

does the function

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)

do a repeated start ?