Fri Feb 4 13:12:17 EST 2011
3V input on 5V circuit.
I need to sniff a 3V SPI bus. I only have 5V boards. What's the
fastest way to interface? For now it's only 3V -> 5V but near future
might need reverse too.
* Build a 3V board.
* Some inverter chip tricks?
It seems it's going to be far easier to just stick to 3V3 for the
sniffer. PIC 3V3 pins are 5V tolerant.
See figure 26-3 in the 18LF2620 data sheet. At 3V3 max speed is about
20 MHz. It should be straightforward to modify the clock settings on
the 2620 to do this.
I tried with a 3V3 cable but didn't work. Voltage measured 4.3V so
maybe I messed up the voltage regulator in the cable? Check here .
The logic levels are 3.3 but the power is 5V. Both 3V3 cables are the
same. Why is that? Ok, going from 4.7 -> 5.0 when using a powered