Not able to read SPI and COM PORT access denied

[Adrian1504]

Hi,

I am developing an application to read the ADXL355 via SPI. I have not been able to read the register of my accelerometer. And I don't know why. 
I tried reading the register of the device ID, but I still got 0. Maybe it is a hardware problem.
I built the application and suddenly I was not able to print messages to the port anymore "COM3: Access denied".
I checked the device tree file and I see this messages, I am not sure if these are the cause of not being able to read the registers and of the com port error:



I will also add a zip file of my project in case it is useful.

2664.SPITry9.zip

Thank you very much.

Adrián Lopez Vudoyra.

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Edit, I restarted the computer and the COM Port works now. I am still not able to read the registers. I tried reseting the device first and then reading, but it is still not returning anything. I thought of it being a hardware problem, but wouldn't it return an error at some point in the init()?

[Adrian1504]

Hi Susheel,

Thank you so much for your reply. I will try to get an oscilloscope or a Logic Analyzer and post the results so that we can continue with this debugging. 

I was going through the datasheet (SPI diagrams) of the BME280 from the intermediate course and compared a little with the datasheet from the ADXL355. I noticed that the R/W bit for the ADXL355 goes in the end:

ADXL355:

BME280:

Should I modify something in my program with this?

Thank you.

Adrian Lopez Vudoyra

[Naeem Maroof]

Hi Adrian,

Thank you for going through the datasheets and making comparisons.

Yes, indeed, that would be the case and you will have to update the code accordingly.

For example, (BME Example from the intermediate course),

you can see that for writing, the 8th bit [b7 from b7...b0] is set as 0 in line 103 while for reading it is left 1.

So yes, please make suitable changes as per your own sensor and datasheet.

Regards,
Naeem

[Adrian1504]

Hi Naeem,

Thank you so much for your answer!

So for me it would have to be tx_buf[] = {(0x00 & reg),value}, right?

And for reading tx_buffer & (void *)?

Thank you,

Adrian Lopez Vudoyra

[Naeem Maroof]

it should be:

//For writing
//0 will be inserted through shift left operation
//otherwise, you can also do the & operation with 0xFE (that will set b0=0)
uint8_t tx_buf[] = {(reg << 1), value}; 

//For reading
//setting b0=1 through OR operation
uint8_t tx_buffer = ((reg << 1) | 1); 

please test as per your own code.

[Adrian1504]

Hi Naeem,

Thank you so much! Now I am able to read some registers! 

I appreciate the help and the patience! 

Adrian Lopez Vudoyra