[SOLVED] NRF24L01 CE and CSN pin loading PIC

[Mrunal Ahirrao]

Hi,
I am working on NRF24L01+(PA and LNA) version. But while experimenting with it I found that the CE and CSN pin of NRF is either loading PIC RC1 and RC2 pin. I am saying "loading" because when NRF is connected the output voltage of PIC RC1 pin(connected to CE of NRF) goes to 1.35V and same with PIC RC2(connected to CSN of NRF) also with voltage of 1.35V and if I remove module from PIC connection then these pins RC1 and RC2 goes to 4.89V. Because of this the NRF don't work in RX mode as CE pin turns out to be 1.35.
is it possible that CE and CSN pin could load microcontroller I/O? I am using PIC18F452. I am applying 3.42V on NRF24L01+(VDD)

 

[ahmed-agt]

Your RF chip was powered with 3.4v while the pic chip uses 5v.is this correct about your connections.

 

[FvM]

Following the datasheet specification strictly, > 3.6 V input voltage is only allowed if Vdd is in the 2.7V to 3.3 V range, so the operation conditions described in post #1 might have already damaged the chip. I have no experience with this specific chip and don't know if damage by slightly exceeding of maximum ratings is likely. I would rather expect that a more serious overvoltage event has destroyed the chip. Or could it be soldered incorrectly, causing shorts with other pins?

 

[Mrunal Ahirrao]

Hi,
Thank you for your help. Actually the problem was that I got an counterfeit chip of NRF24L01+. and I have decreased voltage to 2.91V now. I have also contacted Nordic for this and they concluded me with that the chip I am using is counterfeit.

 

[betwixt]

See the sub-note in section 5.6 (page 18) of the data sheet. You can only use 5V drive signals if the NRF24L01 VDD is between 2.7 and 3.3V.

Personally, I would use a resistive divider to drop the 5V levels to 3V anyway. The cost is almost nothing and it removes the risk of overshoot or supply variations causing trouble.

Brian.