10 Nov
2013
10 Nov
'13
1:51 a.m.
As you mentioned, you'll need a level converter
because no one speaks 5v
anymore. That's also pretty easy to overcome; try some of the '244 and
'245
variants from the 74LVC family. They're very
cheap.
I have had a look at the datasheets for the 74LVC244 and 74LVC245 and,
although I can see how to use them to convert from 5V to 3.3V, I am not sure
I understand how to use them for the opposite conversion from 3.3V to 5V.
The datasheet (http://www.farnell.com/datasheets/1635559.pdf) for the 245
does include the statement "5-V Input/Output Voltage With 3.3-V Vcc ", but I
can't see how the device "knows" the output is 5V or 3.3V.
Also, and here my lack of electronic design knowledge shows through, it says
"OE should be tied to VCC through a pullup resistor; the minimum value of
the resistor is determined by the current-sinking capability of the driver".
I have no idea how to determine the "current-sinking capability of the
driver" so don't know how to calculate the value of the resistor.
Any advice appreciated.
Thanks
Rob