3.3v signals to 5v signals

[Ron Marcus]

Depending on the PIC and port pin, a "1" will be any voltage over 1.8 to 2 volts. 3.3 will look like a "1", not a "0". If the PIC is not seeing a "1", something else is wrong. Check the "Tris registers, and if you want to prove the trip point of the PIC yourself, hook a 10K potentiometer to B+ and ground.Next hook the wiper to the pin in question. Write a short program to turn on a LED when the pin goes positive(and off when a zero).Next, measure the voltage.If it's over 3 volts, I'll buy the coffee!

[dhouston]

At least on the PICs I use the hardware SPI pins have Schmidt Trigger buffers and need 0.7*Vcc (3.5V @ 5V) for a logic high.

[Luciano]

Hi,

Some links.

Best regards,

Luciano

Interfacing 3V and 5V applications:
http://www.semiconductors.philips.co...otes/AN240.pdf

Voltage Level Conversion:
http://focus.ti.com/lit/an/swra071/swra071.pdf

* * *
5V to 3.3V and back from 3.3V to 5V
(Works down to 1.5V)

74LVC4245A Octal dual supply translating transceiver; 3-state
http://www.semiconductors.philips.co...LVC4245A_5.pdf

MAX3370/MAX3371 logic level translators
http://pdfserv.maxim-ic.com/en/ds/MAX3370-MAX3371.pdf

More level translators from Maxim:
http://para.maxim-ic.com/cache/en/results/5043.html

* * *

5V to 3.3V
Inputs can be driven from either 3.3 or 5 V devices.
(The 74LVC125A and 74LVC244A will not replace the 74LVC4245A or the MAX3370/MAX337).

74LVC125A:
http://www.semiconductors.philips.co...4LVC125A_4.pdf

74LVC244A:
http://www.semiconductors.philips.co...LVCH244A_4.pdf

[InitialDriveGTR]

Ok, I successfully got it to receive data using a LVC chip. Now, I have a GPS (CW20 from Navsync - email them for free samples - you just need an antenna) and it has a very vague data sheet. My oscilloscope says it is operating it's serial output at 1.8v. How do i get the PIC to see that? I think a loop back with a max233 might work

[Luciano]

Hi,

Use that:

MAX3370/MAX3371 logic level translators
http://pdfserv.maxim-ic.com/en/ds/MAX3370-MAX3371.pdf

The devices accept VCC from +2.5V to +5.5V
and VL from +1.6V to +5.5V, allowing data transfer
between low-voltage ASICs andhigher voltage devices.

Best regards,

Luciano

[InitialDriveGTR]

Wow, thanks for your help all