uMIRF and PRU pin

Wireless & IoT
1

Hello,

Im trying to connect the uMIRF.

Question is this:

The PRU pin in the uMIRF datasheet it says

"When the PRU is held high, the uMIRF functions normally.

When the PRU is held low, the unit goes to sleep and no inputs are recognized. PRU is held high through a 100k resistor. This pin can therefore be left open if not needed.

"

This seems to contradict itself. Do I have to use the pin? Do I have to set it to high so its always on? Or does the PCB already have that 100k resistor which does that?

Another question. I’m using 68HC11 which uses 5V logic. Can I somehow interface it to this uMIRF which uses 3.3V ?

2

you dont have to worry about it because it is tied internally high

5v - 3.3v

i did the following using a cmos 4050 buffer chip to interface

my rf24g to a 5v atmel may be of use to you

http://www.avrfreaks.net/index.php?name … ic&t=30576

lin

3

that’s exactly what I’m trying to do.

So my plan now is:

the 68hc11 development board is on 5V.

I could take that, connect it through a LM2937 voltage regulator (which gives 3.3V output). This would be the input to the RF module and the CMOS4050.

OR

Having another power supply connected to the LM2937 voltage regulator which would supply the RF module and the CMOS4050.

But then I think I would have to connect the grounds from the 68hc11 board and the RF module together. (I think). And its kind of pointless I think to have to power supplies for a single module.

I think the first idea is a little better.

Any comments?

4

Im using a serparate power supply to run the 3v3

module and cmos converter but that is just cause i have

spare pwr sups lying around it may be less noisier but

i have no proof of this

definitely tie all the grounds together