What is the best board to make a simple usb gamepad? It need to work on iOS, iPadOS, macOS, Windows and Android
It might be nice to research which option is on the market, and then analyze how it works. Maybe a gamepad that can be multi-operating system should have communication via Bluetooth, so possibly the ESP32 would be a good option for prototypes, but for mass production devices maybe there are other chips that are cheaper.
As you mention the use of the USB port, then maybe there are chips similar to the CH341 or from another manufacturer like FTDI, which offers some support for drivers, besides working with USB devices requires a license.
While USB Host does not require a license, research well, some manufacturers may offer chips with a built-in license under some conditions of use, such as keeping identification codes, these codes are what make the hardware manager of the operating system show the information of hardware that the driver will show to the user.
There are plenty boards that provide HID functionality. I can not say if it will work with every operating system.
Some factors that might determine your choice
- Number of required pins for buttons and so on and how much additional hardware you want to add if the number of pins is insufficient. The Arduino Due has the highest number of pins.
- Form factor; boards like SparkFun Pro Micro and, to a lesser extend Arduino Micro, are quite small. They have a limited number of pins that you can expand by using shift registers and/or (SPI or I2C) port expanders and (for analog inputs) multiplexers.
There are other board choices like the Teensy famiily.