esp32

MiSTeryNano FPGA companion ESP32 variant

This is the variant of the MiSTeryNano FPGA companion firmware for the ESP32-S2 and ESP32-S3.

USB Support

You need an ESP32 variant with native USB support, preferrably through a second USB connector. Such a board has two USB-C connectors, one usually being labeled COM and servicing a USB UART (COM port) as typical for ESP32 boards and the second one giving access to the ESP32's native USB port which can be operated in USB host mode to connect a device like a keyboard or a mouse.

Currently the ESP32-S2 and ESP32-S3 are supported. Still, USB support on these devices is rather limited and only one directly connected USB device is supported. Hubs are not supported and thus the use of a (wireless) keyboard/mouse combo device like the Rii R8 makes the most sense for a retro home computer setup. This does not leave a port for a USB joystick which will instead have to be e.g. a retro joystick connected directly to the FPGA.

Hardware modifications

Most ESP32 boards that come with two USB ports are designed to be powered from one of three power sources: The COM USB, the native USB or an external 5V power source, but no to provide power to any of these.

For this project it's preferred if the whole setup can be pwoered from the COM USB port providing power to other USB devices connected to the native USB. Furthermore the FPGA may also be powered from this source. Some boards have solder jumpers e.g. labeled USB OTG and IN-OUT which can provide this. On other boards it may be necessary to remove/bridge diodes.

Features and limitations

• Requires an ESP32 variante with USB host support (ESP32-S2 or S3)
• Only one USB device possible (no hubs)
• Can provide wireless network connectivity (not yet implemented)
• Can provide support for Bluetooth peripherials (not yet implemented)

Building

Get the esp-idf as explained here and install the toolchain:

git clone -b v5.2.2 --recursive https://github.com/espressif/esp-idf.git
cd esp-idf
./install.sh esp32s2,esp32s3
. ./export.sh

You'll then need to make a few adjustments:

First specify which CPU you are using. Either

idf.py set-target esp32s2 

or

idf.py set-target esp32s3 

Then in esp-idf/components/fatfs/src/ffconf.h you need to manually set

#define FF_USE_STRFUNC 1
#define FF_FS_EXFAT    1

Then enter the menu by

idf.py menuconfig

and change a few settings:

• Navigate into Component Config and then into FAT Filesystem Support.
  • Activate the Enable fast seek algorithm ... option
  • Set the Sector Size to 512
  • Set Long filename support to Long filename buffer in heap
• Navigate to Component Config and then to Wear Leveling
  • Set Wear Levelling library sector size to 512
• Navigate to Component Config and then to FreeRTOS and Kernel
  • Set configTICK_RATE_HZ to 1000

Finally start the build with

idf.py build

If successful the resulting binary can be flashed:

idf.py -p /dev/ttyUSB0 flash

Additional debug output is sent via UART at 115200 bit/s

Pin usage

Pin	Signal	Description
TX	UART_TX	Serial debug output
GPIO20	USB D+	USB PIO host D+
GPIO19	USB D-	USB PIO host D-
GPIO14	IRQn	SPI interrupt from FPGA
GPIO13	MISO	SPI data from FPGA
GPIO12	SCK	SPI clock to FPGA
GPIO11	MOSI	SPI data to FPGA
GPIO10	CSn	SPI chip select to FPGA

Example wiring