Read register issue using nrf52 TWI

RE: Read register issue using nrf52 TWI

MartinBL — Mon, 16 Oct 2017 13:21:49 GMT

Happy to help and glad it works.

RE: Read register issue using nrf52 TWI

Shahid Ali Nadaf — Fri, 13 Oct 2017 16:02:53 GMT

Oh Yes....Then its right..i was actually looking at an old datasheet which the company had shared with me along with their development kit...!!!!

Thank You

RE: Read register issue using nrf52 TWI

MartinBL — Fri, 13 Oct 2017 11:54:20 GMT

Are you sure it is not supposed to be 0x02? According to this datasheet I think what you see is correct:

RE: Read register issue using nrf52 TWI

Shahid Ali Nadaf — Thu, 12 Oct 2017 19:54:25 GMT

Hi martin,

Sorry for the late reply, I was caught up with some other work. And Thank you the register read i think is working fine. In order to enable I2C on AS3955, /SS pin of AS3955 should be pulled low which i was already doing in the code using

nrf_gpio_cfg_output(SLAVE_SELECT_GPIO);
nrf_gpio_pin_write(SLAVE_SELECT_GPIO, 0);

but looks like i have to add a delay of 10ms(or less) in order to stabilize I2C pins(i am actually not sure why). Adding the delay of 10ms after writing to GPIO actually worked for me.

nrf_gpio_cfg_output(SLAVE_SELECT_GPIO);
nrf_gpio_pin_write(SLAVE_SELECT_GPIO, 0);
nrf_delay_ms(10);

The default value at register address 0x3E(0x1E) is 0x01(according to datasheet) but for me it reads as 0x02. But i tried reading other registers and all read correct values.

RE: Read register issue using nrf52 TWI

MartinBL — Thu, 05 Oct 2017 07:39:51 GMT

I see. Are you able to read anything other than 0xFF from the other registers? Do you have a logic analyzer or oscilloscope so we can see what is actually going on on the bus? Since you receive 0xFF I assume neither the tx or the rx functions return any errors?

RE: Read register issue using nrf52 TWI

Shahid Ali Nadaf — Wed, 04 Oct 2017 15:56:29 GMT

Hi Martin,

The address is actually 0x1E and the default data contained by 0x1E register(version control) is 0x01. If you look into the datasheet I2C access modes contain 3 bits to set the mode and remaining 5 bits contain the register address. For register read the Mode bits should be set to 001 and the remaining 5 bits are occupied by the register address(0x1E), hence it is 0x3E.

Mode bits Register Address
M2 M1 M0 C4 C3 C2 C1 C0
0 0 1 1 1 1 1 0

Therefore the address is 0x3E (otherwise the actual address is 0x1E in the datasheet)

RE: Read register issue using nrf52 TWI

MartinBL — Wed, 04 Oct 2017 12:42:05 GMT

What kind of data is stored at address 0x3E? I couldn't find any reference to that particular address when skimming through the datasheet.