Problems with the SPI SCK on the nRF51822 in SPI Slave Mode

[James]

Hi,

I'm trying to connect my nRF51822 PCA100001 development board to a ARM M3 processor via the SPI. In this case the ARM M3 is the SPI master and the nRF51822 is the SPI slave. I'm using the spi_slave_pca10028 SPI example as my starting point for setting up the nRF51822 as the SPI Slave. I do not have a SoftDevice programmed on the nRF51822.

When I enable the nRF51822 SPI by setting the NRF_SPIS1->ENABLE and send a SPI packet from the Master to the Slave my SCK seems to get cut in half when viewing it on the scope.

When the nRF51822 SPI Slave is disabled and I send a SPI packet from the master to the slave my SCK clock range is from 0V - 3V.

When the nRF51822 SPI Slave is enabled and I send a SPI packet from the master to the slave my SCK clock range is from 1.3V - 3V. So it looks like enabling the SPI slave on the nRF51822 is messing with my SPI SCK.

Have you encountered this problem?

Thanks!

[Stefan Birnir Sverrisson]

Hi

Make sure the two boards have the same ground. Also make sure that your PCA10001 board has revision 2 or revision 3 of the nRF51822 chip. The first revision did not have SPI slave, only SPI master. The nRF51 compatibility matrix maps nRF51 chip markings with nRF51 chip revision.

[James]

Hi Stefan,

Thanks for taking a look at my question. I checked my nRF51822 chip markings and I have the following nRF51 chip on my development board.

N51822 QFAACA 1230AA

From looking at the compatibility matrix and reading the nRF51822 PS v1.3 associated with this nRF51 chip revision it looks like this chip is Revision 1. So it doesn't have the SPI Slave peripheral. Can you please confirm this?

Thanks!

[Stefan Birnir Sverrisson]

Hi Brian

Yes, I can confirm that you have the first revision of the nRF51 chip which does not have any SPI slave. I would recommend for you to get the nRF51 DK instead which has the latest nRF51 third revision.

[James]

Thanks Stefan for all your help. We've ordered more nRF51 development kits and made sure we have the third revision of the chip on them.

[Stefan Birnir Sverrisson]

Hi Brian

I am glad that we have figured out the cause for your problem. I am looking forward to assist you with any potential future questions when you receive the new kits.