Comments for using RPi with SPI memory

Ok!

I have learned that I should use pins 24/26 as CE0/CE1 instead of pin15(GPIO 22) because this alleviates me writing extra code. I plan on using Python SPIDEV from GitHub...

Thanks for Elektor Academy - Hardware Hacking the RPi pointing this out. Excellent if you want the details

Question: What to do with HOLD pin? I need it to stayhHigh. Also how to make the CS pin be high but go low when transmitting?

Thanks,

Clem

Hi Clem,

Use a pull-up resistor (10K should be just fine) with the HOLD pin.

The CS handling is done by the driver.

I found an example here involving MCP3008. This chip uses an active low chip select as well as the 23K256. Good luck!

Just to be clear:

V3.3 ------- R1(10K) -------- HOLD

What state is the CS when I boot up? I put power on the 23K256 and the bootup for the Pi goes crazy with strange errors. Take power off the 23K256 and no problem...

Thanks

Yes, you are correct about the HOLD pull-up resistor.

As for the CS state, I have to check it on my board as well. Can you try to disconnect the SO pin of the 23K256? Of course, this means the SPI communication with this chip won't work but it is worth checking if this is the cause of the strange errors you're seeing.

With the pullup resistor on HOLD, I can boot RPi with power to SPI memory. Thanks @bbolo1 !

Clem

Hi Clem,

Congrats!!! It is good to hear everything works fine with the SPI memory. Good luck with the tests!

After you play with SPI maybe you can try some I2C chips as well. There are so many interesting I2C chips (pressure, temp, acceleration sensors, gyros, magnetometers, ...) you can attach to the RPi.

Hi Clem,

Congrats!!! It is good to hear everything works fine with the SPI memory. Good luck with the tests!

After you play with SPI maybe you can try some I2C chips as well. There are so many interesting I2C chips (pressure, temp, acceleration sensors, gyros, magnetometers, ...) you can attach to the RPi.

Well I am stuck again, but this time I think software. I can program using python, but nothing gets stored(?) and the chip does not respond (0XFF) ! If I unplug the chip's +3 volts, all responses are 0X00... I am too close to this to figure it out. Ask me questions to send me on the right track.

Thanks,

Clem

You've now reached the stage where I would connect the 4 channel scope or a logic analyser !

Do you have either ?

If not you can try posting your code and we'll see if we can pick our way through it.

MK

HI @bbolo1

     No scope (Yet), but have voltmeter and was thinking to use over SO/MISO and ground. It is also a current meter as well. Will do some I2C next after this works.

Thanks,

Clem

Well post the code here and I'll see if I can pick my way though it.

If you are bit banging the SPI you can add logging features to the code to trace each pin state as it runs.

MK

Well guess what...

I decided to pull everything and remount changing colored wires and new positions and the thing is working! So cannot tell what is wrong!?! I have a few bit flips, but that may be timing or something. But progress is being made. Thanks for the help. Next is a code rewrite/cleanup because so much extra stuff

Clem

I'm glad it's working - how fast are you running the spi clock and how long are the wires ?

Any chance of a picture ?

MK

Sure I will sum this up experiences and all. Thanks @Michael Kellett for kind words of encouragement