Tested on STM32F401CC board but not work

[tomzbj]

There should be something wrong with my configurations.
Could you please make a full example, including the initialization of gpios & timers? I'll check mine.

[b-dmitry1]

Sure! Fortunately, I found STM32F401CCU6 in my garage, so now I need a few days to assemble a board and test it.

[tomzbj]

Oh thanks. I think there wouldn't be many differences between STM32F401 and other STM32F4s. Your previous project should be ok.
I have also F407 and F446 boards, later I'll try them.

[b-dmitry1]

Done! Added full demo to my "stm32" repo. Please check stm32/examples/softusb.
I use Logitech K120 keyboard + mouse.
Chip: stm32f401ccu6 on a DIY board.
Crystal: 8 MHz.
USB-Serial converter is connected to Uart1 pa9/pa10 pin.
Please keep the wires as short as possible - I used that long wires only to test the connection quality.
I tested it only on Windows arm-none-eabi-g++ and didn't tried on Linux -> the Makefile should be edited.

[tomzbj]

Sorry for late reply. I changed the gpios to pull-down. Then it worked very well with wired keyboards and mice, but still couldn't recognize a logitech wireless mouse and a mechanical-switch keyboard. I guess they simulated themselves as usb composite devices.
I also tried this: https://github.com/sdima1357/stm32f103C8T6_USB_HOST. It could support 4 usb ports at the same time, and supported joysticks. But its code is too messy. I prefer yours.

[b-dmitry1]

Thanks :)
Yes, I didn't managed to make a wireless devices work too.
Maybe the library should be upgraded for a full-speed device and hub support.

Receiving and transmitting bits at 12 MHz via differential lines using a STM32 @ 72 MHz clock may be a bit tricky:

• A first idea was to use RS485 differential transmitter and a SPI port but there's a problem with transmitting EOP bits (2 zeroes) and 9-bit chars (NRZ requirement).
• A second idea was a 2 SPIs working in parallel, but I don't know how to properly trigger transmit/receive simultaneously.
• A third idea was to use a DMA directed to GPIO pins. We can create a byte array with any number of encoded bits including EOP, and send it at 12 MHz rate using DMA. This should be fast and reliable. But I didn't tried this before and don't know is it really possible. Don't know how to make DMA-to-GPIO work at 12 MHz.

A full-speed USB host has huge benefits: USB multiport hubs, hard disks, fast HIDs, and many more.

What do you think? Any idea may help.

[tomzbj]

I tried DMA to GPIO before. If you use M2M mode, it would be very slow, 20 clock cycles per move or even slower. M2M mode can't make the bus work at full load.
But you can use DMA-SPI or DMA-DAC modes instead, just change the SPI or DAC peripheral address to your GPIOx->ODR. Then it should be much faster, maybe 6 or 8 clock cycles per move.
I made a dds signal generator with GD32F303CC (originally 120MHz), and overclocked it to 240MHz. (Its extreme clock could be up to about 320MHz.) The dds refreshing clock could be 24MHz, 1/10 of SYSCLK.
Link: https://github.com/tomzbj/diy/tree/master/2022/gd32_dds

[b-dmitry1]

Wow, good work! Thanks for the information!
Just tried stm32f105 - in memory-to-ODR mode there are 11 clocks per move so we have only 6.54 mbits/s @ 72 MHz CPU clock. So stm32f1x will not work.
Then, I tried stm32f401 @ 84 MHz:

  TIM1->CR1 = 0;
  TIM1->DIER = 1 << 8;
  TIM1->PSC = 0;
  TIM1->ARR = 2;
  TIM1->CR1 = 1;

  for (;;)
  {
    dma->CR = (6<<25) | (10<<11) | (1<<10) | (1<<8) | (1<<6);
    dma->PAR = (unsigned int)&GPIOA->BSRRL;
    dma->M0AR = (unsigned int)buffer;
    dma->NDTR = sizeof(buffer) / sizeof(buffer[0]);
    dma->CR |= 1;
    // ...
  }

And the frequency was 12.000 MHz. You're absolutely right.
So it is possible to achieve 12 mbits/s required for Full speed communication on a 84 MHz stm32f4 microcontroller.

The algorithm:

1. Unpack bytes to NRZ bits in a byte array.
2. Point DMA to this array and send it at 12 MHz rate to a GPIO.
3. Reverse DMA direction.
4. Start probing bus, and when D+ change its state start DMA transfer immediately.
5. Pack NRZ bits to bytes.

Right?

[tomzbj]

I guess so, but I am afraid that 84M is still not fast enough.
Another way, maybe you can try DMA-SPI mode, use MOSI pin to output NRZ bits?
I tried this mode to output VGA signal, like this guy: https://www.artekit.eu/vga-output-using-a-36-pin-stm32/