SPI not working with MBED (was: Performance of XIAO with Sharp Memory Display)

Products & Technology XIAO
#21

No, I use D10 for MOSI and D8 for SCK as per https://how2electronics.com/wp-content/uploads/2022/05/Pinout.jpg

I used D4 for SS since I don’t think it makes a difference which one I use?

I had the oled and already tested it in real life. The project depends on being sunlight readable and fast update (so no eink) and the OLED was literally invisible.

#22

Oh, you mean when using softSPI? Yes, I did use 4-6 then

#23

Since D8 and D10 are hardware SPI pins, why don’t you try using pins other than D8 and D10 in software SPI configuration.

#24

sorry I was late, see above. I used D4-D6 for soft SPI.
Or maybe not. It’s late and I’m tired, need to try tomorrow.

#25

Ok resoldered to test it.

#define SHARP_SCK  6
#define SHARP_MOSI 5
#define SHARP_SS   4

Adafruit_SharpMem display(SHARP_SCK, SHARP_MOSI, SHARP_SS, SCREEN_WIDTH, SCREEN_HEIGHT, 2000000);

I get around 2Hz like this when using MBED :frowning:
Around 10Hz non-mbed (which would be okay, but using non-mbed still makes me rewrite the whole bluetooth-code which I honestly don’t understand how to… :frowning:

#26

Let’s call it a day.
I don’t have Sharp on hand, so I am limited, but I will give it some thought.

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#27

I set the clock to 2 MHz and checked the waveform again. 1 byte transfer time is
mbed : 24uS
non-mbed : 8.5uS
The throughput of mbed is about 1/3. The frame rate difference may be the correct result.

I’m also working on a “2-peripheral” version using non-mbed, but I do not even know if it is possible to expand to “2-peripheral” in the first place. I still need more time.

#28

You mean using the Bluefruit-library?
I think there is even an example for this in Adafruit Bluefruit NRF52 libraries → Central → central_bleuart_multi

I may give it a go in the next hours as well…

#29

would you expect the hardware SPI on mbed to work normally or also slowed down? I mean, do you expect the limitation to only affect soft SPI?

#30

so I just integrated everything into my codebase again and switch back and forth between hard and soft SPI.

Using soft SPI, I get around 1.5Hz, with hard SPI, I get almost exactly 9Hz - which would look good enough, if I would get any output using the hard SPI-pins.

If you PM me your address, I’m going to gift you one.

#31

You mean using the Bluefruit-library?

Yes.
It is a totally non-mbed prototype, but I was able to connect two peripherals and transfer data. Still needs to be debugged.

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#32

Using soft SPI, I get around 1.5Hz, with hard SPI, I get almost exactly 9Hz - which would look good enough, if I would get any output using the hard SPI-pins.

According to the data sheet, the frame frequency is 20 Hz when the clock frequency is 2 MHz. mbed’s hardware SPI throughput is 1/3, so 9 Hz should be sufficient.
Just to confirm, it’s 9Hz in mbed, right?

#33

Wow, that’s awesome. I would be ready to test and help debug.

#34

exactly, yes. 9-10 Hz using mbed and hardware SPI (which shows no output).

#35

(which shows no output)

What do you mean? Does it mean it doesn’t work?

#36

that’s my main problem yes :slight_smile:
mbed and SPI never produced any output to me with the Sharp-display.
I only know the framerate because I log it to the console.

#37

The prototype will be sent by e-mail as soon as it is ready. Please forgive me for the prototype. The comments are in Japanese for the most part. The data is simply millis() and battery voltage.
I would be really happy if you could debug it and use it!

Sorry, I have started a project to connect multiple peripherals to a PC.
I will look into the limitations of mbed’s SPI a bit more.

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