Using a voltage divider, any problems?

General discussions about V-USB, our firmware-only implementation of a low speed USB device on Atmel's AVR microcontrollers
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capcom2
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Joined: Wed Aug 29, 2012 10:23 pm

Using a voltage divider, any problems?

Post by capcom2 » Wed Aug 29, 2012 10:28 pm

Hi guys,

I just wanted to run something by you guys, as I am working on implementing V-USB on my ATMega8 for the first time.

To get the 3.3 - 3.6 V voltage on D- and D+, would it be alright to use a voltage divider type circuit?

I plan on using a 330 ohm resistor for R1, and 470 ohm for R2 with a 5 V source. That would give me a voltage of roughly 3.5.

I haven't seen too many reports of people using a voltage divider, which is why I wanted some insight.

Thanks :)

ulao
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Re: Using a voltage divider, any problems?

Post by ulao » Sun Sep 02, 2012 2:56 pm

using a voltage divider limits the pull-up voltage only. Signal levels generated by the processor wont get touched. The signal levels need to be near the right levels. See the USB spec.

horo
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Location: Berlin & Lindau, Germany

Re: Using a voltage divider, any problems?

Post by horo » Mon Sep 03, 2012 10:24 am

Hi,

Regarding the voltage divider solution we had a discussion two years ago with detailed calculation of hi and lo levels:
http://forums.obdev.at/viewtopic.php?f=8&t=1352&start=45#p16316

Ciao, Martin

anders89
Posts: 2
Joined: Thu Feb 28, 2013 7:36 pm

Re: Using a voltage divider, any problems?

Post by anders89 » Thu Mar 07, 2013 6:28 pm

Hi capcom2,
Have you completed your MIDI project, can you provide me some details about this project ?

full turn-key pcb

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