USB to Serial converter using AVR microcontroller

Posted on Monday, June 9th, 2014 in AVR, USB by DP


Yet another great project by Dr. Ayman Shalaby of Electronics Lab, a USB to Serial converter using an ATMEL AVR microcontroller:

This project is a USB to Serial converter using an ATMEL AVR microcontroller. There are two version of the converter, one with SMD parts and another with TH parts. The mcu used is an ATmega8 and USB communication is done using software on AVR mcu. It’s based on the software USB implementation of AVR-CDC. Firmware can be downloaded from the download section of CDC-RS232.

This entry was posted on Monday, June 9th, 2014 at 1:00 pm and is filed under AVR, USB. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

7 Responses to “USB to Serial converter using AVR microcontroller”

  1. KH says:

    My apologies to Dr. Ayman Shalaby, who I am sure is very enthusiastic at embedded design. However, the last two blog postings about Dr. Ayman Shalaby’s great projects have a big flaw — is there actual working hardware? It’s nice to see the 3D display, or the schematics or the PCB layout, but has the thingies been actually validated? Actual working devices and working well, with software working well too? All too often, there is actually plenty more to do between finishing a PCB layout and getting an actual board to run its firmware to expectations. I would rather see finished or working projects, however messy they look, than a rendered 3D object.

  2. I noticed the schematic shows a 16Mhz crystal. The 12Mhz version of the v-usb code seems most stable (thousands of Chinese USBasp programmers use 12Mhz), hence I would suggest 12Mhz instead of 16.
    And since 12Mhz falls in the 3.3V power abilities of the AVR, you could consider running the AVR at 3.3V and get rid of the zener diodes. I’ve seen people posting about problems with some 3.6V zener diodes, perhaps due to the added capacitance.

  3. Dr Ayman Shalaby says:

    All my designs I finished it with working projects EgyDuino , USB to serial , etc
    I will upload a real images of the working projects soon with videos .

  4. Dr Ayman Shalaby says:

    @Ralph Doncaster (Nerd Ralph)
    You can use 12 or 16 MHz crystal with appropriate firmware , I tried both is working fine , there is a version of TH design try it and even on breadboard

  5. ee says:

    This thing is such a bodge. It is running off “something less than 5V” because there is an LED in series with the supply to the microcontroller. Then, since it is still too high, there are zener diodes on the USB data pins. As for what voltage is present on the serial interface, who knows.
    And as for the badly drawn schematic.. rule #1 is never cross wires and draw a junction. I see it is violated.

    • Dr Ayman Shalaby says:

      This thing is working fine , if you make some effort and try it even in a breadboard you will make a good idea about it .
      The badly drawn schematic , I did not notice where is rule #1 ?
      I think you are talking about another schematic ,

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