is V-USB for Esp8266 possible?

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is V-USB for Esp8266 possible?

By robotmaker42
- Tue Mar 01, 2016 2:50 pm #42186 Ok so there are tons of tutorials on how to setup v-usb for the arduino, with the use of some zenner diodes and some other comments. the digispark supports v-usb right off the bat. The problem is that these boards run on 5v and the esp8266 runs on 3v. I havnt been able to find any tutorials on how use v-usb with a 3v micro-controller. I know that some arduino boards support actual usb 2.0 but v-usb is bit-banging usb 1.0. could some one help figure out how to use the esp8266 for v-usb. I figure this is mostly a hardware question and not a software(5v vs. 3v).
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Re: is V-USB for Esp8266 possible?

By RichardS
- Tue Mar 01, 2016 3:08 pm #42188 Also been wondering!

I run lots of 3.3V Cortex M3 on USB and they all work!

I have been wondering if there is crazy timing that is required??

If its popular to do I can start a section for it.

RichardS
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Re: is V-USB for Esp8266 possible?

By martinayotte
- Tue Mar 01, 2016 3:17 pm #42190 The zener diode on AVR V-USB are used because the USB bus specification requirements are that data lines be 3.3V.
So, that won't be an issue for ESP, you won't need such zener diodes. So, no question about hardware.
Yes, V-USB is only for USB 1.1.
The biggest challenge is on software side : since ESP as only 1 core and that WiFi thread is particularly tricky, receiving the USB interrupts with proper critical timings can lead to some issues. It doesn't mean that it is undo-able, but maybe issues will be difficult to deal with. I think it is better to have hardware solution, either the one currently used such CH340 and the others, or simply to attach an AVR such as ATtiny85. There are also High Speed USB 2.0 compatible bridge such as CY7C68013, or even CYUSB301X, and several others.
That all depends of what is your project ...
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Re: is V-USB for Esp8266 possible?

By RichardS
- Tue Mar 01, 2016 9:39 pm #42214 Yes that is what I was thinking also, could be tricky... if you did not have the TCP-IP and WIFI stack to deal with at the same time! :|

RichardS
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