Author Topic: 3.3v logic to 3v and visaversa  (Read 2053 times)

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Offline GeirTopic starter

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3.3v logic to 3v and visaversa
« on: January 24, 2008, 04:12:04 AM »
I i'm building a robot, using the spartan3 starter board. And im connecting it to a BISMS02BI bluetooth modul. The problem is that the bluetooth module is operating at 3v UART logic and the spartan3 at 3.3v.

Any one got any good ideas?
$50 Robot schematic http://elektro.russemotto.com

Offline benji

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Re: 3.3v logic to 3v and visaversa
« Reply #1 on: January 24, 2008, 05:08:43 AM »
if the data is only oneway (from 3.3 to 3 volts sending) u can use an interface circuit like a fixed gain stage (op amp) to transform 3.3 to 3 volts.
or by using a zener diode.
good ol' BeNNy

Offline GeirTopic starter

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Re: 3.3v logic to 3v and visaversa
« Reply #2 on: February 07, 2008, 12:25:48 PM »
fixt it whit a simple diode :) Got some strange curves but it works, tanks :)
$50 Robot schematic http://elektro.russemotto.com

Offline brijesh

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Re: 3.3v logic to 3v and visaversa
« Reply #3 on: February 07, 2008, 10:24:39 PM »

First check that is the max input voltage that the bluetooth module can handle, usually most devices can handle couple of 100mV above supply voltage just fine. If the max input voltage is lesser than 3.3, just put series resistor for any signals flowing from spartan3 to the bluetooth module.

Better solution just run spartan at 3V, pretty sure it will be just fine.

Brijesh

Offline GeirTopic starter

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Re: 3.3v logic to 3v and visaversa
« Reply #4 on: February 08, 2008, 07:43:25 AM »
You cant run the spartan3 card at 3v :( And i checkt te output from the card on a scope it was up in as mutch as 3,8v. And series resistors vont work cuz the bluetooth current is not static. But a diode worked just fine.
$50 Robot schematic http://elektro.russemotto.com

 


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