Intan RHD2164 with NRF52840 (SPI) - Double Data Rate Issue

[quenmasc]

Hello,

  I hope you are well.

 I am currently working on interfacing an INTAN RHD2164 chip with the NRF52840. This chip is connected in SPI with the NRF52840. The only problem is that it works in Double Data Rate. I have already tried interfacing with the SPI but nevertheless reading on the MISO line in double data rate is not possible with the single SPI Mode. Therefore, I was wondering if QSPI in dual mode would do this. I enclose the technical documentation for reading SPI. Any suggestion would be welcome.

Regards

Quentin

[Simon]

I don't think you will be able to use QSPI to communicate with the RHD2164, since it uses SPI (with DDR) which is a different protocol. SPI uses two separate data lines for input and output (MISO and MOSI) while the QSPI interface uses four data lines and configures the lines to output/input on the fly. The RHD2164 datasheet says the following:

"Note that this DDR technique is a non-standard mode of SPI communication and will likely require an FPGA to implement."

However, I came over a workaround that might work: https://www.esp8266.com/viewtopic.php?p=66519#p66519 

Best regards,

Simon

[quenmasc]

Hello Simon,

  Thank you for your very enriching answer which allowed me to understand something that I did not know, it is very appreciated!

  One last question for my understanding, is it the CLK of my SPI that I configure to twice the speed it should be at SLAVE (intan)? In fact, given the SCK required for the Intan chip, it would be better if I use the SPIM3 which allows 32MHz SCK?

Best Regards,

Quentin

[Simon]

quenmasc said:

One last question for my understanding, is it the CLK of my SPI that I configure to twice the speed it should be at SLAVE (intan)?

From my understanding, the speed on the master (52840) side should be twice the speed required by the slave (intan).  

quenmasc said:

In fact, given the SCK required for the Intan chip, it would be better if I use the SPIM3 which allows 32MHz SCK?

Yes, it seems like SPM 0-2 does only support data rates up to 8 Mbps 

• https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf52840%2Fspim.html&cp=4_0_0_5_24_5&anchor=topic
• https://devzone.nordicsemi.com/f/nordic-q-a/43600/spim-speed

, so if the speed on the INTAN RHD2164 is 16 Mbps, you need to use SPIM3, to get a speed of 32 Mbps

Best regards,

Simon

[quenmasc]

Hi Simon,

 Thanks you for your time ! Help me a lot !

Regards

Quentin