nRF52832- why when using nrf_drv_spi with an ADXL362 I need to set the clock in high drive (H0H1)

[Cyril Praz]

Hello!

I am working on a project. The goal is to retrieve every seconds some acceleration data from the ADXL362 accelerometer.

I configured the spi in blocking mode by passing NULL as event handler nrf_drv_spi_init(_spi, &_spi_config, NULL);

This method will use the information inside the _spi_config structure to set the pins with this configuration:

PIN_CNF[MOSI] = 0x00000003
direction:output, input: disconnect, pull: disabled, drive: S0S1, sense: disabled

PIN_CNF[MISO] = 0x00000000
direction:input, input: connect, pull: disabled, drive: S0S1, sense: disabled

PIN_CNF[CLK] = 0x00000001
direction:output, input: connect, pull: disabled, drive: S0S1, sense: disabled

PIN_CNF[SS] = 0x00000003
direction:output, input: disconnect, pull: disabled, drive: S0S1, sense: disabled

But when I try a dummy transaction like read (0x0B) the register with the acceleromter ID (0x00), I should have 0xAD.

Instead I have this:

S0S1.JPG

I thought that The MISO pin was not really disconnected but after several tries I found that if I modify the clock pin config to work in high drive:

PIN_CNF[CLK] = 0x00000301
direction:output, input: connect, pull: disabled, drive: H0H1, sense: disabled

I have now a good communication transaction with the accelerometer:

H0H1.JPG

Any idea why the clock config influence the MISO signal?

My project need to be low power, therefore I should not use the clock pin in high drive mode.

Another guy have the same problem: devzone.nordicsemi.com/.../

Thanks for your help,

Cyril Praz

[airshaven]

I have the similar issue when using adxl362.I got a reply of 0x00 instead of 0xad when read register 0x00. based on your suggestions, I drive CLK pin to H0H1, but nothing improved. then I also driven MISO pin to PULLUP. I received 0xbf that was incorrect. using a oscilloscope, i found once MISO pin pull up. it never pull down again.do you have any idea about it?

[Cyril Praz]

It's hard to say wha tis wrong do you have a screenshot of your oscilloscope?

Be careful about the alimentation of the ADXL362 -> www.dropbox.com/.../aaaefefef.JPG

if the voltage go under the minimum voltage you should be sure that the voltage is 0V before turning on the alim of the ADXL362

[airshaven]

i get problem solved.but i still have some confuse.could you move you step to nRF52832 read ADXL362 chip id.