TRF7970A: IRQ does not occur

Hi Utku,

first of all you should check all the voltages at the TRF7970A device if they are as specified in the datasheet. Another possible fail could be the oscillator. Please check if the oscillator is running at 13.56MHz or 27.12MHz depending on the crystal used.

Best Regards,

Helfried

Voltages are ok, the oscillator is running at 13.56MHz, but there is no IRQ signal, its in idle state. 

Hi Utku,

I can only assume that there is a problem with the communication  to the TRF7970A. Even if there would be a problem in the RF part, then at least, when TX is finished (FIFO empty) an IRQ must occur.

Best Regards,

Helfried

Hi, we've observed the IRQ line from the power-up of the board, there is no change at the signal, it is always in idle state.

Hi Helfried,

The same problem still persists. We see problems with hundreds of cards. We had to stop production. Can you help in more detail? I am sending the logs of our working and non-working cards in the attachment. I can provide the schematic and layout if you can provide an e-mail address.

working rfid.log

not working rfid.log

Hello Utku,

Helfried is out of office until 9/27/2021.
I'm not an expert, but from your log file it looks like you have trouble to communicate to the TRF7970A.
It seems that it never comes to the point of TX, which would fit to your missing IRQ observation.
Have you referred to chapter 6.10 in the data sheet (https://www.ti.com/lit/gpn/trf7970a) for your SPI control?
It might also help to record the SPI signals with a logic analyzer (similar as in thread https://e2e.ti.com/support/wireless-connectivity/other-wireless-group/other-wireless/f/other-wireless-technologies-forum/1037909/dlp-7970abp-trf7970a-initialization-and-write-read-registers-via-spi).

Best regards,
Andreas.

Hi Andreas,

Thank you for your support. I can post detailed scope outputs tomorrow. However, according to the output I have, we observe a strange behavior in miso when CS drops to low. It couldn't follow CS and go low right away. What is your opinion about such behavior?

Hello there. I'm getting a few more scope outputs. Our same TRF7970A module board works with MSP430. But it doesn't work on TI's linux driver. We did not make any changes to the driver. Do we need to make any changes to the driver? Do you have any advice? The situation is very urgent because mass production is at a standstill.

As far as we can see from the logs, we get a 0xFF response to the TRF7970A_CMD_TEST_EXT_RF (0x99) command. Then the device tries to init repeatedly. We keep getting 0xFF from MISO to the 0x83 command recursively. 

Faulty device (0x83 command -> Reads 0xFF):

Is there anything wrong that you see from the scope screen?