Communicate with MAX30100 Sensor using TWI

[emircankavas]

Hi,

I want to read and write MAX30100's registers. How can i do that? I tried a lot of solutions but I didn't solve that.

For example; MAX30100's address is 0x57. And I want to initialize this sensor. So I should this: (pseudo code)

write_to_register(0x57, 0x06, 0x02); // write '0x02' to '0x06' register

write_to_register(0x57, 0x09, 0x02); // write '0x02' to '0x09' register 

write_to_register(0x57, 0x07, (0<<2)|4); // write '(0<<2)|4' to '0x07' register

read_from_register(0x57, 0xFF); // read '0xFF' register (should return 0x11 according to datasheet)

How can i do that? Can you help me please?

[Jørgen Holmefjord]

Hi,

Have you had a look at the TWI sensor example in the SDK? This example show how to write and read data from TWI sensors.

Note that reading a register normally requires you to first write the register address to the TWI device, and then read back the response.

Best regards,
Jørgen

[Jørgen Holmefjord]

Are you sure that you use the correct TWI address for the sensor? You can scan the TWI bus for sensors using the TWI scanner example. The example will output the address of any TWI devices found on the bus.

You should normally write the address of the register you want to read, but this should be described in the datasheet of the sensor.

[emircankavas]

I used scanner at Arduino and adress is 0x57. And datasheet says for part ID:

In this case if i want to read 0xFF adress, I should write 0xFF to 0xFF first then i read?

[Jørgen Holmefjord]

Yes, that is correct and is shown at the bottom of page 25 of the device's datasheet. The MAX30100 also seems to expect no stop condition between write and read operations, meaning you should set the no_stop parameter to nrf_drv_twi_tx call to true when performing a read operation.

[emircankavas]

I changed no stop parameter to true but problem is not solved. If it helps here is my code: sdk11.7z

My code is in examples/peripheral/twi_sensor/pca10028/arm5_no_packs/

Code output:

[Jørgen Holmefjord]

You need to check the error codes returned from your calls to write_single_register/write_registers/etc., to make sure you get a successful transfer or if you get a timeout. In your twi_handler, you set m_xfer_done, while in the transfer functions you wait for twi_tx_done/twi_rx_done flag. 

[emircankavas]

Yes when i am using nrf_drv_twi_rx, it gives me NRF_ERROR_BUSY error. How can i solve this? Should i edit twi_handler function?