Couple things on USB that might help.
You can easily buy a TTL to USB converter.? Takes TTL level (as from uart/usart) signals, either 3.3 or 5.0 volts, and translates them to a USB signal.? That USB signal, when plugged into a PC, enumerates as a serial port.? You set the baudrate at the terminal to match the TTL baudrate.
In a number of microprocessor boards (my experience is with the ST-MICRO boards), the USB chip on the board used for programming also has a virtual terminal function (at the same time as debugging).? The USB chip is hardwired to a USART output on the processor.? If you don't use those pins for something else, and don't disconnect them, you can initialize that particular USART on the processor and use it to communicate through the debugging cable.? Your debugging system runs an instance of a terminal program.
In addition, if you enable the fprint functions in your system and direct them to the USB usart channel, you can get ongoing outputs from the processor to the computer for monitoring a process.? You could also use the console in and out functions, but those may need to be redirected in your program.
Really easier than you might think.
As to emulating a true HID device, I haven't tried that, haven't needed to, but I suspect with the right drivers, emulating an HID device (mouse, etc) might be easy enough.
Harvey
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On 12/2/2021 12:07 PM, Chris Wilkson via groups.io wrote:
This is fantastic work, Holger!
I have a disembodied P7001 that I keep meaning to add to a 7704 so I can play with it. Or, finally accept that I will never get to it and pass the p7001 to a new owner.
Your project tilts my internal debate toward "keep it". :)
Quick question on Teensy: Can it be configured as a USB HID host?
I have many homebrew projects that would benefit from a USB keyboard-to-TTL converter but I'm honestly intimidated by USB complexity so I haven't done much research on USB hosts.
