hi
in my project i use an altera kit that works at 3.3Volt.
in my the project i send data from the computer directly to the altera (this part works) via the LPT port. the problem is that i need to send data back to the computer from the altera but the altera works at 3.3v and the computer works at 5v.
what can i do?
thank you for your attention

 

If you have the option of open-collector signalling, you can use pullup resistors to 5V. Otherwise, you can use a level shifter.

This is a pretty good read...

 

first i want to thank you for your help
second i dont know if you understood that i am using one cable for the communication so any thing i do should work both ways. and if its relevant
and third do you have an example for a bi-directional level shifter
and last thing whats open-collector signalling???
and again thank you very much
AND sorry for all the and

 

Try ULN2803 and adding 8 pull up resistors.

 

There lots of transceiver ICs designed to do this...

 

App Note on bi-directional level shifters

If your bus is going to be input for one cycle, say, when strobe is enabled, and strobe is disabled for the incoming data, then a 74HC245 is easily used and low cost.

If you don't have a way to sense/synchronize direction on a wire, such as an I²C bus, you'll need to read the app note linked above.

 

What altera chip are you using? Some Altera chips are able to handle 5 volt

 

What altera chip are you using? Some Altera chips are able to handle 5 volt

It's probably a FPGA or CPLD with LVTTL I/O... If that's the case, the device cannot respond at the 5V level.

 

It's probably a FPGA or CPLD with LVTTL I/O... If that's the case, the device cannot respond at the 5V level.

I know very well what Altera is. I asked because some of series can be made 5 volt tolerant with only a resistor. And other like the MAX 3000 may have 5 volt tolerant pins. I guess the OP uses the Byteblaster download cable ore a clone of it. As it is very simple. By the way here is low cost USB Altera programmer clone using a PIC micro. With some help of Google translate I was able to build one my self. And yes it works http://www.sa89a.net/mp.cgi/ele/ub.htm

 

I know very well what Altera is.

I didn't explain what Altera is...

I asked because some of series can be made 5 volt tolerant with only a resistor. And other like the MAX 3000 may have 5 volt tolerant pins.[...]

The OP has already conveyed that the device is 5V tolerant(or at least the pins used are) in that the LPT can transmit to the Altera device properly. The problem is transmitting from the 3.3V device to the 5V device.