While some of the earlier and slower arduino boards had 5V TTL, it’s worth looking at some of the newer boards that have hardware serial ports…if you stick to certain pins. It’s also worth the trouble for buffers/level shifters and using something like a PJRC Teensy, with some examples having numerous IO pins, and a processor that can run up to 600 or 700 MHz (can be run slower as desired). You can still use the familiar arduino IDE. As another option, you can use visual studio with the visual micro plugin for arduino.

If you should use visual micro, you might need to enable a flag for something in its settings, if you’re going to generate C++ code. It’s free. If you want the in circuit debugging, a license is only $30.