MiRF (Arrrgg) frustration

Wireless & IoT
1

Hi,

I am struggling to make the MiRF’s work, I would really appreciate any comments from someone with similar expecience.

I have a pair of nRF2401 based MiRF’s. I am using a AVR tiny2313 as a uC. The software is very similar to the posted examples. I . I am using a 16bit CRC. My config word is the same as used in the example, except that I am running at 250kbps in Shock Burst mode. I used a 24 bit address.

Here is the problem. I am receiving data when I am not transmitting. As long as the MiRF has a clock source available when DR1 goes up, it clocks out garbage. The voltage on the DATA pin is all over the place from -2vdc to +2vdc. I have used RF bypass caps on all of the VCC’s. I have turned off the LAN, shut down my PC, turned off the mircowave.

I have a few questions that perhaps someone might be able to shed some light on.

  1. Is it normal to have the baseline voltage on the DATA pin of the MIRF wildly fluctuate all over the place from -2vdc to +3vdc when in receive mode? That is, CE is high. It looks fine during configuration, but goes nuts when it monitors the air for signal.

  2. Does the nRF2401 check the address of incoming signal against the address in the config word before it declares data ready? Would I be advised to use a 40 bit address? Would that help filter out garbage?

  3. DR1 goes low after the uC clocks out the data (the garbage, that is). It stays low for 25-200 uSec (varies) then DR1 and the voltage on the DATA pin both go high together (exactly together). They are not connected in any way (except inside the MiRF). Is this behavior normal?

Any comments would be sincerely appreciated.

Jim Lake

2

Jim,

Welcome to the club. Lots of posts in this forum about getting started with MiRF.

24-bit address and 16-bit crc is very selective. My guess is you are not in shock

burst mode. Had similiar problem until I got the config writes working. Try changing

your config to direct mode and see if there is a difference.

My guess about the “+/-” voltages would be a missing ground.

George

3

The problem with the wild voltage turned out to be a scope coupling mixup. That is solved. I will check the config word again, and try normal mode.