3.3 volts
I have a stamp activity board with bs2.
·Has anyone ever run both or just a bs2 on 3.3volts
I would like to do some serout to another module for a quick test.
Larry
·
·Has anyone ever run both or just a bs2 on 3.3volts
I would like to do some serout to another module for a quick test.
Larry
·
Comments
Leon
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Post Edited (Mike Green) : 10/23/2009 11:51:58 PM GMT
Use a voltage divider on the output of the BS2 to drop to 3.3volts. A singal 2N2222/or MPS3904 can amp up 3.3volts to 5volts for a BS2 input
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
The Truth is out there············___$WMc%___···························· BoogerWoods, FL. USA
I know I am not the only one; any points on the subject might help others...
Thanks in advance
Larry Stroud
On page 43 of this·PDF·(see Fig. 45) you will find the recommended circuit for interfacing 3V circuits to 5V circuits.· I'm sure that somebody will pop off about using a resistor or something.· There's the right way to do things and then there are short-cuts, quick-fixes, et al. ·(N.B., the road to Hell is paved with good intention.)
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- Stephen
sparkfun, bob-08745, logic level converter, 1.95 each
I ordered a few its easer than trying to put the smoke back in!
These things are about 1/2 inch long x 1/4 inch and there four channels in one package
Two low voltage to high voltage and two high voltage to low voltage
It would cost more to buy a transister than this complete package.
The Parallax pressure sensor (VTI SCP1000) implements the SPI interface, and there are separate pins for input and output. So for the stamp output to VTI input you can use two resistors to step down the voltage, to the SCLK and MOSI signals:
or replace the 20kOhm resistor with a zener. On the input side, from the VTI MISO, the Stamp will respond fine to 0 to 3.3 Volt inputs, because the Stamp switching threshold is near 1.4 Volts. You will need a voltage regulator to supply the 3.3 volts to the VTI chip. There are also chips that can do the level translation, such as the CMOS CD4050, which can be powered from 3.3 volts and give 3.3 volt outputs, but also take 5 volts on the inputs.
Other more modern chips implement essentially the circuit shown in the pdf that PJ mentioned. That is suitable for I2C level translation, where there needs to be bidirectional signaling with pullup resistors.
There are some Stamp products that can be set to work directly at 3.3 volts, such the MOBO Stamp, or our OWL2pe data logger.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tracy Allen
www.emesystems.com
Just about any resistor solution relies on using the ESD process diode and will inject unnecessary noise into the IC. Other methods might incorporate a diode to "simulate" an open collector driven output and this works fine, but only if the voltage levels are still the same.
The diagram that PJ Allen refers to is the one that should be used... If you would rather a Bi-polar version instead of the MOSFET version, then the below schematic is basically the Bi-polar equivalent of what PJ is talking about.
Bi-polar version of the Bi-directional 3.3V to 5V Emitter Follower
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 11/13/2009 5:30:55 PM GMT
If the signaling is unidirectional and/or if there is no pullup resistor, things can be simplified. For example, with SPI the simple voltage divider from 5V to 3V, or series resistor from 3V can work fine. The Stamp has plenty of noise immunity when presented with a 0 to 3.3 volt signal at its input.
There should always be protection resistors in case the power supplies come up at different times. That applies also to the mosfet or bipolar circuits that PJ and Beau posted , because of the currents that can flow through the protection diodes if one power supply comes up before the other.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tracy Allen
www.emesystems.com