nrf24 and RFID reader not working together

Here is the situation. I have a parallax RFID reader hooked in and using the software serial lib (I have tried the AltSoftSerial lib as well). This works fine and has been running my door lock for awhile. I deced to add a way to open it using the nrf24 wireless module as well. To do this I hooked it up and got it working in a different project. All was going so well.

I then hooked up the nrf24 and the RFID reader to the same arduino and then I ran in to problems. It seems that when the RFID reader is enabled I can not receive data on the rf24 module. Putting some code in to debug I can see that it is checking for the the data every loop, so nothing is blocking that. If I disable the RFID reader via code or by grounding the enable pin it will start working. As soon as the reader enable pin is brought high again though, it stops.

To fix this I tried switching serial libraries (using AltSoftSerial as stated before) Swiched from using software SPI to hardware SPI and still no luck.

I have used the iBoardRF24 lib for the software spi lib and used the nRF24L01 and RF24 libs found here https://github.com/stanleyseow/RF24 for the hardware tests. I have spent close to 8 hours fiddling with this today, what am I missing?

what am I missing?

A schematic of how you wired it up, and a link to the nrf24 data sheet.

Datasheet http://elecfreaks.com/store/download/datasheet/rf/rf24l01_PA_LAN/nRF24L01P.PDF

I have tried many different ways of wiring it, currently I have the rf24l01 hooked to the spi pins (11,12,13) CE pin 4, CSN pin 10. Using the hardware SPI libs. (When using the software libs I used pins A0-A4 in the following order Sck, MISO,MOSI,CE,CSN)

RFID reader is currently connected to VCC and Gnd, Enable is on pin 6 and sout on 7. I also just tested with it hooked to the hardware serial (pin 0) and still had the same result.

Again, the RFID reader works and the rf24l does not. If I disable the RFID (via software or via grounding out the pin in pin 6) the rf24 starts receiving. Let me know if you need the data sheet to the parallax reader.

What frequency is the RFID reader 125KHz or 13MHz? It could be that the fields are interfering with each other.

To start off try powering them off different power supplies ( common grounds ) and separating them physically as much as possible.

it is 125khz I do believe. I will try separating them physically. I do have them hooked to the same ground and will adjust that as well.

No luck. Still has the same issues.

Got this working. Re-read your post and seen you said to connect it to a different power source and not a different ground. Moved the nrf24 from the 5v pin, that was powering the RFID as well as the nrf24, to the vin pin. That solved it. Now right now I am powering it via 5v so it works. If I move it to battery it will be powered by 9v. Also the final project only has a single power rail in it, will this still have issues? Is this an issue of not having enough current through that port or is it interference of some sort?

It could be a current issue measure what each takes. However it is probbly a supply decoupling issue so the two devices should be heavenly decoupled using both capacitors and inductors.

This looks to me to be a decoupling issue. I have capacitors on my power supply in. two 22uf, one on the in, and one on the out, however this doesn't seem to be enough. I have been researching the issue the last few days but am still a bit lost. Do I need to add another one close to the nrf24 power in and/or the power in to the rfid reader? you mentioned inductors but I am not sure how to set this up. Could you give me a bit more direction and point my research in the right directions? I seem to be spinning my wheels.

Last circuit on this page http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

xlilcasper: Got this working. Re-read your post and seen you said to connect it to a different power source and not a different ground. Moved the nrf24 from the 5v pin, that was powering the RFID as well as the nrf24, to the vin pin. That solved it. Now right now I am powering it via 5v so it works. If I move it to battery it will be powered by 9v. Also the final project only has a single power rail in it, will this still have issues? Is this an issue of not having enough current through that port or is it interference of some sort?

Pls I need u to shed more light on the reason u used a 5v power supply contrary to d 3.3v required for the two modules and also why u decided to use a Vin pin