Minimal arduino to be used for fast serial communication

I noticed when I use the Digispark, serial communication between my computer and the digispark is kind of slow. Or in other words the communication is much faster when I use an arduino nano. I am not an expert but I guess this is due to the USB-To-Serial Chip that is missing on the digispark.

Since I am a fan of minimal circuits I was wondering, how to build a arduino-compatible minimal board that has a usb to serial chip on it. A minimal arduino was reported before, but how could I add the usb to serial chip to this minimal configuration and which one would you use? In the end I would like to program this minimal arduino over usb connection like it's done with any arduino.

What's wrong with the Micro?

The upload speed is hard-coded in the Arduino bootloader, so you won't be able to change that (57kbaud or thereabout, if I'm not mistaken). As for 'normal' serial communication, the Arduino and most Serial-to-USB chips, like FTDI, officially support up to 1Mbps, but in practice, higher speeds can be achieved.

As for the Digispark: handling a USB connection is quite a hard job for such a little chip, maybe that's why it's slower. Other boards, like the Arduino Uno have a separate chip for that.

That being said, I use my 'minimal' boards (Atmega328P + resonator) with a handy little FTDI board, just add a 6-pin header to connect it when needed. I also add a cap and resistor to the RTS pin for auto-reset when uploading. See this page.

It sounds more like you need an FTDI rather than a full Arduino. You are only doing USB-to-serial and aren't processing, converting or filtering the data in any way?

The minimal Arduino with serial communication is an Atmega 328 chip running on its 8MHz internal oscillator. The whole circuit just needs 3 x 0.1µF capacitors and a 4k7 resistor to hold the reset pin high. You can power it from 2 or 3 AA cells or a 3.7v Lipo.

If you want really high serial speeds use an Arduino with a 32U4 MCU (Leonardo or Micro) because they transfer data at the full USB speed and ignore the baud rate.

...R

DrDiettrich did a good point. I think the Atmega32u4 is the way to go, no ftdi chip needed, however it is a little bit more expensive. Thank you everybody for your suggestions.