SparkFun Electronics Forum

arduino or teensy++ can they run at 5v and see a 3v logic input?
The micro teensy++ runs at 5v and where can i find documented that it will work with 3 volt or 3.3 logic input.

The Teensy I/O pins connect to the AVR microprocessor. So the data sheet for that will answer your questions.

see avrfreaks.net - most data sheets are there. Or of course, Atmel's web site.

I am looking at the data sheet I am looking in the pin io section and can't find anything about the thresholds....

I am looking at page 398 30.2 DC Characteristics...
this is what I found...
VIH
Input High Voltage,
Except XTAL1 and
RESET pins
VCC = 2.7V - 5.5V
0.6VCCmin
5v * .6 = 3v so it is questionable with a power supply dip right?
the reg is 3.3v the micro has a 5v reg

Ok but now I ran into another problem the teensy runs at 16mhz 16mips so how do I know what converter is fast enough so I do not have to put delays in my code if I want to say pin up and pin down or visa versa without having to put delays in??? I found these

The bidirectional translator I seen on a comment on sparkfun.com 's
page that has a translator but the comments said it had problems and
used a simple voltage divider for the down converter this was
sugjested in the comments. TXB0108 I am looking into how fast it is.

It is described as 8-BIT BIDIRECTIONAL VOLTAGE-LEVEL TRANSLATOR WITH
AUTO-DIRECTION SENSING AND ±15-kV ESD PROTECTION.
8 channel and said to be 2$ on the post. so less than 2 of these could
isolate and level translate on all the lines needed if it was fast
enough...

here is the link I set the propigation delay on the search to 3ns but
their are some products clasified differently so they may not be in
these results.

http://www.mouser.com/Semiconductors/Lo ... ricing%7C0

josheeg wrote:Ok but now I ran into another problem the teensy runs at 16mhz 16mips so how do I know what converter is fast enough so I do not have to put delays in my code if I want to say pin up and pin down or visa versa without having to put delays in??? <snip>

if you give us a clue as to what you're trying to accomplish, we can probably help you get there.

josheeg wrote:I am looking at page 398 30.2 DC Characteristics...
this is what I found...
VIH
Input High Voltage,
Except XTAL1 and
RESET pins
VCC = 2.7V - 5.5V
0.6VCCmin
5v * .6 = 3v so it is questionable with a power supply dip right?
the reg is 3.3v the micro has a 5v reg

So this tells you that if your input is 3.0V or more it will be a logic 1, with 0.3V of margin. The device producing this signal would be powered by 3.3V regulator, right? So there wouldn't be a "dip"?

There are simple circuits to allow for a pull-up resistor to 5V. Or use of a level shifter chip if you have a number of lines.

Liencouer wrote:

josheeg wrote:Ok but now I ran into another problem the teensy runs at 16mhz 16mips so how do I know what converter is fast enough so I do not have to put delays in my code if I want to say pin up and pin down or visa versa without having to put delays in??? <snip>

if you give us a clue as to what you're trying to accomplish, we can probably help you get there.

Hi I am going for the level converter chips I have over 9 lines I think 12
here is a link to my pre release of the open source hardware I am working on it is being programmed in C because I herd I can get tighter code than the arduino control functions.

http://sites.google.com/site/openloopproject/

I am looking to go from the ads1278 24 bit 20K samples per second on 8 channels simultaniously.
The processor is the teensy++

josheeg wrote:

Liencouer wrote:

josheeg wrote:Ok but now I ran into another problem the teensy runs at 16mhz 16mips so how do I know what converter is fast enough so I do not have to put delays in my code if I want to say pin up and pin down or visa versa without having to put delays in??? <snip>

if you give us a clue as to what you're trying to accomplish, we can probably help you get there.

Hi I am going for the level converter chips I have over 9 lines I think 12
here is a link to my pre release of the open source hardware I am working on it is being programmed in C because I herd I can get tighter code than the arduino control functions.

http://sites.google.com/site/openloopproject/

I am looking to go from the ads1278 24 bit 20K samples per second on 8 channels simultaniously.
The processor is the teensy++

The Teensy++ has 12 available I/O port bits?
Before diving into 8 x 20K sps, at 24 bit datums, consider whether the 8 bit micro has enough RAM, I/O and compute to ingest/process at that rate. What you speak of is quite high.

Yes it has 12 bits or more available.

Before diving into 8 x 20K sps, consider whether the 8 bit micro has enough RAM, I/O and compute to ingest/process at that rate. What you speak of is quite high.

the usb serial example on the teensy++ website I compiled and ran the benchmark example it is fast enough to transmit to do that. Also their is enough speed to interupt or poll data ready read a byte clk read byte clk read byte. Do this till 2 samples filll some of the 64byte usb buffer array put the array into the usb serial out function that does a bulk transfer. I might have the function name wrong.