TWI Master and access to RAM through EEPROM Register

RE: TWI Master and access to RAM through EEPROM Register

Guillaume Exc — Thu, 25 Jun 2020 04:04:23 GMT

It worked indeed i did not understand that we had to write before reading the values. Thanks for the help !

RE: TWI Master and access to RAM through EEPROM Register

Hung Bui — Wed, 24 Jun 2020 12:46:30 GMT

Hi Guillaume,

Please have a look at the example twi_master_with_twis_slave inside \examples\peripheral.
In that example there is an emulated EEPROM is used. And it works almost like the MLX90632. Have a look at eeprom_read() function. First we use nrf_drv_twi_tx() to write the address we want to read, and after that we read it out using nrf_drv_twi_rx . Notice that the no_stop argument was set to true. matched with what described in the sensor datasheet.

Please study section 10.2 in the MLX90632 datasheet.

RE: TWI Master and access to RAM through EEPROM Register

Guillaume Exc — Tue, 23 Jun 2020 02:05:17 GMT

Hello, I don't see any possible way to add eeprom into the nrf_rdv_twi_rx() or nrf_rdv_twi_tx() . When looking at the documentation (here) You don't have any explanation regarding EEPROM reading.

When using for example nrf_drv_twi_rx(), the parameters following the documentation should be :

nrf_drv_twi_t const * p_instance ----> &m_twi
uint8_t address -----> SensorAdress ( in my case 3A)
uint8_t * p_data ------> data
uint8_t length -------> sizeof(data)

And that's it, there is not explanation on how to handle the EEPROM of the sensor and adding the different addresses.

I might misunderstand the function so if you have any way of explaining on how to use theses functions to use EEPROM i would be thankful. For example how should i do if i want to access the eeprom address of 0x3001.

Regards

Guillaume

RE: TWI Master and access to RAM through EEPROM Register

Hung Bui — Mon, 22 Jun 2020 14:17:55 GMT

Hi Guillaume,

I don't see anything special about accessing RAM and EEPROM on the MLX90632. It's defined at section 10.2 in the product's datasheet. You can use nrf_drv_twi_rx() and nrf_drv_twi_tx() to read and write.

RE: TWI Master and access to RAM through EEPROM Register

Guillaume Exc — Sat, 20 Jun 2020 06:29:48 GMT

Hello Hung,

I understand the fact that you can't help much about the 3rd party library but i believe my issue is really accessing the data stored in the eeprom and RAM from the sensor. Is there any template i could relate to because i believe the nrf_drv_twi that you suggested doesn't handle eeprom use.

Anyway thanks for your help

Guillaume

RE: TWI Master and access to RAM through EEPROM Register

Hung Bui — Fri, 19 Jun 2020 13:35:41 GMT

Hi Guillaume,

We can't really help you to interface with a specific 3rd party sensor, however I would suggest you to:

- Use a logic analyzer to capture the TWI transaction and compare it to what you can find in the sensor's datasheet and the sensor's library.

- Try to use TWI directly using nrf_drv_twi it may give you more flexibility than the nrf_twi_sensor library.