On Tue, 07 Aug 2012 18:08:59 -0400 Neil wrote: > Hmmm... was not aware that the USART TX was open-drain, but this can=20 > make things much simpler. I'll have to investigate that. >=20 > FWIW, each line is single direction always -- they are not > bidirectional lines. The line that goes 3.3V-->5V is what I was > worried about, as when the 3.3V TX output goes high, it would only go > up to 3.3V, whereas the 5V RX input wants to see 4.0V. But this is > moot (and solved) if it's open drain. >=20 > I do remember that the 3.3V PIC's RX and TX pins are both 5V > tolerant, but now sure if the 3.3V side will clamp it. I'll have to > test this with my existing prototype setup I think. Even if it isn't open-drain in hardware, you can always make it open drain by shoving a diode in series. That brings you down to two components as well as replacing a 3-pin MOSFET with a 2-pin diode. Chris --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .