I2C problem in nrf51822

RE: I2C problem in nrf51822

Ole Bauck — Mon, 14 Dec 2015 12:09:06 GMT

The address is shifted in the driver, so 0xA6 with write will be clocked out as 0x4C and 0xA7 will be clocked out as 0x4E. The read/write bit is handled by the driver, you should only pass in the address: ADXL345_ADDR (0x53). If nrf_drv_twi_tx is called, this will translate to 0xA6 being clocked out, if nrf_drv_twi_rx is called, 0xA7 will be clocked out.

RE: I2C problem in nrf51822

rushin — Mon, 14 Dec 2015 02:16:26 GMT

ok so should i read rxdata

RE: I2C problem in nrf51822

RK — Mon, 14 Dec 2015 02:11:05 GMT

wait for the callback - read the buffer you sent in.

RE: I2C problem in nrf51822

rushin — Mon, 14 Dec 2015 02:08:39 GMT

ok but how to get read data??

RE: I2C problem in nrf51822

RK — Mon, 14 Dec 2015 00:07:48 GMT

if the rx function isn't calling you back then either the thing isn't sending data because it's not in a mode to send data, or it's not sending 6 bytes of it and the driver is waiting for the rest of it, or you're getting an error. You're likely to have to do a write to tell the device that

you want data
which register you want data from

that write probably goes with the final flag set to true so you get a repeated start and not a new start. Then you send the read, perhaps waiting until the write completes first, perhaps not if the two commands can be buffered after each other.

and that rx_data[] better not be a stack variable if you're passing it to a function because it'll get stomped on as soon as you return.

RE: I2C problem in nrf51822

rushin — Sun, 13 Dec 2015 17:08:13 GMT

return value of function nrf_drv_twi_rx is NRF_SUCCESS or NRF_ERROR_BUSY. then how to read data and store it in array

RE: I2C problem in nrf51822

rushin — Sun, 13 Dec 2015 17:01:50 GMT

i know that sequence. but this sequence

ret_code_t err_code;

uint8_t rx_data[6];
err_code = nrf_drv_twi_rx(&m_twi_adxl_345,ADXL345_ADDR_RD, rx_data, sizeof(rx_data), false);
APP_ERROR_CHECK(err_code);

give me nothing data

RE: I2C problem in nrf51822

RK — Sun, 13 Dec 2015 14:57:37 GMT

well I assume for reading you first do a write, with the flag set to true, then you do a read which reads back the data. The datasheet on the device should tell you the sequence you need to read from a register, it must be something like write to the register, then read data from the chip.

RE: I2C problem in nrf51822

rushin — Sun, 13 Dec 2015 13:05:42 GMT

can you explain me twi event handler

RE: I2C problem in nrf51822

rushin — Sun, 13 Dec 2015 12:45:55 GMT

thanks i understand nrf_drv_twi_tx function.but i can't understand nrf_drv_twi_rx function. if i want to read 6 byte data from 0x32 address??

my code is like

ret_code_t err_code;

uint8_t rx_data[6];
err_code = nrf_drv_twi_rx(&m_twi_adxl_345,ADXL345_ADDR_RD, rx_data, sizeof(rx_data), false);
APP_ERROR_CHECK(err_code);

how to store this 6 byte data and how to start reading data from perticular address like 0x32?

RE: I2C problem in nrf51822

RK — Sun, 13 Dec 2015 11:59:22 GMT

can you use the code button (which really just indents every line by 4 spaces) to format that so it's readable and looks like code please, in that state it's just impossible to even see what you're trying.

I answered something similar a few weeks ago devzone.nordicsemi.com/.../ was the question