nrf21540 SPI communication voltage level problem

[Dominik Eugster]

Hi

I connected the nRF21540 to a nRF52840 like in the application notes.

Here is the schematic:

I implemented the driver and now I try to communicate over the SPI with the nRF21540.

First, I try to read the Partnumber. When I set the power dowen off, the SPI signals are ok, but of course I have no feedback from the MISO.

yellow is the SP I Clock, green is MISO, orange is MOSI, lila is ChipSelect

Signals ok:

As soon as I set PowerDown = ON = nRF21540 enabled, the second SPI MOSI pulse is there, but really low (nRF21540 pulls down the level!)

What is the reason of this and how this can be solved?

Reagrds

[Dominik Eugster]

If I set the ChipSelect line manually to low without the SPI driver functions, the 0x94h is transferred correctly, even there is no feedback from the  MISO line, why? commnd 0x94 is correct, isn't it?

0x94 = 0b1001 0100

= 10 (read) and 010100 = 0x14 = PartNumber

[Dominik Eugster]

And if I use the nrfx driver, the MOSI signal switch back to high level with a courve, I think there is a bug on the nRF21540 or the driver? Please get in contact asap.

[Dominik Eugster]

Now with the MISO PullUP setting, the MISO line is high,but still without any feedback...

// <o> NRFX_SPI_MISO_PULL_CFG  - MISO pin pull configuration.
 
// <0=> NRF_GPIO_PIN_NOPULL 
// <1=> NRF_GPIO_PIN_PULLDOWN 
// <3=> NRF_GPIO_PIN_PULLUP 

#ifndef NRFX_SPI_MISO_PULL_CFG
#define NRFX_SPI_MISO_PULL_CFG 3
#endif

[Dominik Eugster]

is it possible, that nRF21540 doesn't answer if its not in the UICR Program Mode? Even if I read something like the PartNumber?

Edit: -> not the solution, same problem

Is there a reference plot of the SPI signals or an example project for the nRF21540-DK, to measure this by myself?

[JONATHAN LL]

Hi Dominik,

The nrf21540 does not need to be in UICR program mode to red part number. As you can see in table 1 here.


Needs to be in program mode(PG).

Regards,
Jonathan