subbu pillai

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7 years, 2 months ago.

SPI read to KS8995 Ethernet chip always return FF

Hi,

I have connected KS8995 Ethernet switch to my Raspberry PI SPI. Ok. Trying to read the register of KS8995 using spi driver ioctl calls. I am using spidev_test.c program for that. I tried both /dev/spidev0.0 and /dev/spidev0.1, to read the register of KS8995 via SPI. It is always returning FF. Here is the code link for spidev_test.c https://github.com/KnCMiner/spi-test/blob/master/spi-test.c. I am giving input as [01, 02] to read registers 01 and 02. uint8_t default_tx[] = { 0x01, 0x02]

The output is alyways FF for any register. Could you please tell me where I going wrong.

Thanks Subbu.

1 Answer

Sanjiv Bhatia
7 years, 2 months ago.

Hi subbu. Not sure how this is related to mbed but, have you seen this webpage ?

https://www.raspberrypi.org/documentation/hardware/raspberrypi/spi/README.md

The Raspberry Pi is equipped with one SPI bus that has 2 chip selects.

The SPI master driver is disabled by default on Raspbian. 

To enable it, use raspi-config, or ensure the line dtparam=spi=on
is not commented out in /boot/config.txt, and reboot. 

If the SPI driver was loaded, you should see the device /dev/spidev0.0.

The SPI bus is available on the P1 Header:

MOSI    P1-19
MISO    P1-21
SCLK    P1-23   P1-24    CE0
GND     P1-25   P1-26    CE1

What is your pinout between the raspberry PI and your external SPI device ?

Are you sharing a common ground ?

External device is being powered correctly ?

If you do not have one already, consider to pick up a low cost SPI bus analyzer - many are available for under $ 10 USD and use the tool to assist to debug and observe the activity on the SPI port pins.