3v to 5v level translation

[Scott Miller]

I'm connecting a 5-volt HD44780 LCD controller to a 3-volt microcontroller.
I'd planned to use a level translator IC, but I just switched to an MCU with
5-volt tolerant inputs. Actually, I don't need inputs - just 6 outputs. My
question is this - assuming the slew rate is acceptable, is there any reason
I can't just connect each I/O line to a pullup to 5 volts, set the port to
all 0's, and then use the data direction register to switch between
high-impedance input mode and output to control the 5-volt signals?

Seems to me like it should be fine, but I can't recall having seen it done
that way before.

Thanks,

Scott

 

[Joe.G]

Some HD44780 Coppies Can run at 3V but the V0 LCD cross the LCD glass needs
to be 5V.

So the copy IC can direcly interface to your 3V MCU.

JG
"Scott Miller" <scott@3xf.com> wrote in message
news:110kh9kkcjo0t18@corp.supernews.com...

I'm connecting a 5-volt HD44780 LCD controller to a 3-volt
microcontroller.
I'd planned to use a level translator IC, but I just switched to an MCU
with
5-volt tolerant inputs. Actually, I don't need inputs - just 6 outputs.
My
question is this - assuming the slew rate is acceptable, is there any
reason
I can't just connect each I/O line to a pullup to 5 volts, set the port to
all 0's, and then use the data direction register to switch between
high-impedance input mode and output to control the 5-volt signals?

Seems to me like it should be fine, but I can't recall having seen it done
that way before.

Thanks,

Scott