Now I am using ATMEGA328P and want to communicate with computer in serial using B connector female (also want to provide power from computer to ATMEGA328P using B connector).

So here is my question. How can I connect D+ and D- to ATMEGA328P's pin No. 2 (PD0/RX) and pin No. 3 (PD1/TX)? In other words which pin should I connect to D+ and D- ? Also is it possible to connect them directly?

Thank you in advance.

  • 1
    Have you examined the schematic of an Arduino device that uses the '328P? Nov 1 '17 at 2:21
  • I have seen the schematic of Arduino but they connect D- and D+ to ATMEGA1602. But this time I want to use ATMEGA328P only.
    – zalt
    Nov 1 '17 at 2:44
  • 1
    Did you ever stop to wonder why they do that? Nov 1 '17 at 2:45
  • I'm not quite sure, maybe due to converting. But now I am asking is it possible doing that with ATMEGA328P only?
    – zalt
    Nov 1 '17 at 2:54
  • Pull up the datasheets for both devices; you don't need the complete datasheets, just the summary datasheets will do. Examine and compare the front pages. Nov 1 '17 at 3:49

The Arduino Uno (and similar boards) have a chip on them that does serial communication via a dedicated USB chip (the ATmega16U2 chip). You can't just connect pins 2 and 3 to D+ and D- and turn that into USB.

You can conceivably do it using V-USB which does USB in software in conjunction with a few extra components.

You can also buy external serial to USB adapters which do the conversion externally. If you Google serial to usb adapter you will find quite a few for around $3.

  • The Adafruit Trinket Pro adafruit.com/product/2000 uses this, so does the usbasp (not Arduino code) fischl.de/usbasp @zalt, if you have to ask, don't do this. I has special requirements for the hardware and software, and it is something for advanced engineers. Stay away from it.
    – Jot
    Nov 1 '17 at 10:57
  • ok I did with HID-class USB Serial Communication for AVRs using V-USB. I could monitor the incoming data to PC by HID Serial Monitor. However, I need to monitor the incoming data by Serial monitor such as tera-term or Arduino's serial monitor. Is there anyway to do that with HID-class ? I tried trinket-fake-usb-serial, but did not work at all. Please I need help.
    – zalt
    Nov 9 '17 at 7:05
  • This sounds like a different question to me. First you ask if certain ports can be connected to a USB device, now you are asking about monitoring serial data with a HID-class USB. I suggest you make a new question. Offhand, using a HID (Human Interface Device) when there isn't a human there clicking away seems like a misuse of the hardware.
    – Nick Gammon
    Nov 10 '17 at 6:44
  • All I want to do is just getting the serial data from MCU(ATMEGAA328P) to PC without using serial to usb adapter.
    – zalt
    Nov 13 '17 at 2:39
  • The Atmega328P doesn't have a USB interface so what you want isn't really practical. There is no "simple wiring" that will achieve that.
    – Nick Gammon
    Nov 13 '17 at 6:07

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