It was a hardware defect. With a new board with 500 ohm resistor in series it works perfectly. Thanks a lot for thinking along @MicroController!

Thanks, I've tried that by putting a 1.2K resistor in parallel to the 10k on the mosfet (3v3 side). This compares the 10k+1.2K situation (white line) to the stock of just 10k (blue). I do see that the curve starts to bend at around 2.5V, which is also around 0.75 * VDD, the high-level input voltage ...

I just tested with the ESP32-S3-DevKitC-1 using my signal generator and it works fine on that one. I also found that the ESP32-S3-MINI-1 has a resistor on the U0TXD line internally, so I guess that might filter out some glitches and that's why it works?

I also looked at lowering the clock of the ...

Yes, I have the correct SPI mode selected (3, CPOL=1, CPHA=1).

I tested, the interrupts are not the problem. When I provide my own CS with the generator it still has the same issues with the SPI peripheral counting one clock too many, sometimes.

Reducing the interrupts is a nice improvement indeed. It was on my list but low prio, since it does not seem to hurt ...

I've created two test projects to demonstrate the issue. One of them generates the signal and the other one reads it:
* https://github.com/hberntsen/mhi-ac-spi ... -generator
* https://github.com/hberntsen/mhi-ac-spi-signal-tester

MicroController I've put an interrupt on the CLK signal that resets a timer. When the timer reaches 1 millisecond that means the clock is idle and I toggle the CS. I originally did that by physically connecting two GPIOs together, that is now done internally through the GPIO matrix (using the ...

What genuis decided it'd be a good idea to connect the same USB data lines to two USB connectors plus two other connectors, then also put pull-up resistors on them, label them as "TX" and "RX", and wire them together to two IO pins each?! That board is a mess!

As the webshop says:

A USB-A ...

Hi,

I'm running into a problem: on the ESP32-S3, using the SPI slave often generates transactions with too many bits received. In a rare case I get less bits.

* It is a 30KHz clock with 160 or 264 bits of data (configurable), sending 20 transactions per second.
* The code is over here: https ...