NRF24l01+ radio module in a low voltage scenario - Page 1
Forum section: electronics / projects

author: JJalling
author_rank: Unknown
timestamp: February 19, 2016, 08:43:31 pm
content: Hi all,Does anyone on the forum have experience with the NRF24l01(+) chips? - especially when running on low voltage.I'm currently using some cheap modules from ebay to test them out, but the plan is to integrate the RF part on the main PCB of my project, later on.According to the datasheet, the module is able to run down to 1,9V (page 13,http://www.nordicsemi.com/eng/content/download/2726/34069/file/nRF24L01P_Product_Specification_1_0.pdf), so my plan was to power the circuit from a coin cell. My problem is, that the module stops transmitting, when the voltage gets bellow 2,8V (running from a bench PSU). Am I misunderstanding something, or shouldn't I be able to run it bellow 2,8V?Have a nice weekend!BR Jonas

author: JJalling
author_rank: Unknown
timestamp: February 19, 2016, 09:32:43 pm
content: Ok, this is embarrassing.. I did some more debugging and found that the problem was not the NRF module.On my pcb, there is also a device connected via an i2c bus. I was relying on the internal pullups in the micro, to pull up the bus. This doesn't seem to work on lower voltages, so the program was waiting for a response in the i2c bus, before transmitting the result via the radio, but never got a response from the other chip.After populating the pcb with the pullups, I can get the radio to transmit down to 1,7V.BR Jonas

author: Pack34
author_rank: Frequent Contributor
timestamp: February 19, 2016, 09:38:01 pm
content: With I2C it's always advisable to not rely on internal pull-ups.

author: wraper
author_rank: Unknown
timestamp: February 19, 2016, 09:40:08 pm
content: FYI cheap NRF24l01 modules contain counterfeit NRF24l01 IC.http://zeptobars.com/en/read/Nordic-NRF24L01P-SI24R1-real-fake-copy

author: JJalling
author_rank: Unknown
timestamp: February 19, 2016, 10:20:03 pm
content: Quote from: Pack34 on February 19, 2016, 09:38:01 pmYes, I know, but because I'm running of a single CR2032, I try to reduce the current draw as much as possible.BR Jonas

author: JJalling
author_rank: Unknown
timestamp: February 19, 2016, 10:21:04 pm
content: Quote from: wraper on February 19, 2016, 09:40:08 pmYes I'm aware of that. The modules from ebay are just for testing. The final design will be with components from a distributor.bR Jonas

author: Fungus
author_rank: Super Contributor
timestamp: February 19, 2016, 10:34:37 pm
content: Quote from: wraper on February 19, 2016, 09:40:08 pmWow! Coolest chip die ever? Look at all the weird stuff going on in there:Anybody know what's going on?

author: MarkF
author_rank: Super Contributor
timestamp: February 20, 2016, 02:19:10 am
content: I'm currently working with the nRF24L01+ modules too.I'm using a pic16f877a MCU at 5V to communicate with the nRF. I found that when running the nRF at slightly under 3V, I was dropping packets. 3.0V seems to be the minimum for the PIC. A 0.1V made all the difference for me. Also, I've not been able to get the Enhanced ShockBurst to work.You do know that the nRF module is SPI and not I2C.

author: TheDirty
author_rank: Frequent Contributor
timestamp: February 20, 2016, 02:30:33 am
content: Quote from: Fungus on February 19, 2016, 10:34:37 pmNot an expert in this, but the pretty hexagons are on chip inductors.

author: JJalling
author_rank: Unknown
timestamp: February 20, 2016, 08:26:52 am
content: Quote from: MarkF on February 20, 2016, 02:19:10 amAccording to the datasheet, your pic shouldn't be able to go down to 3,0V. The datasheet says 4,0V for the non-L version. But if you get the L version, you should be able to get down to 2,0V if you keep your clock at max 4MHz.I got my nrf module to work downto 1,7V.BR Jonas

author: MarkF
author_rank: Super Contributor
timestamp: February 20, 2016, 09:09:32 am
content: Quote from: JJalling on February 20, 2016, 08:26:52 amYou miss understand. My PIC is running at 5V and the nRF24L01+ is running at 3V. I had problems with the nRF running at 2.9VMy limit is what the PIC considers as the minimum voltage for a logic '1'.

author: JJalling
author_rank: Unknown
timestamp: February 20, 2016, 10:16:14 am
content: Quote from: MarkF on February 20, 2016, 09:09:32 amAhh Ok. Yes the nRF datasheet says that if the input signals to the module is above 3,6V, the nRF supply voltage should be between 2,7V and 3,3V.The reason I'm able to run it at 1,9V, is because the output from my microcontroller is bellow 3,6V.BR Jonas

author: Zero999
author_rank: Super Contributor
timestamp: February 20, 2016, 12:59:59 pm
content: Quote from: TheDirty on February 20, 2016, 02:30:33 amIt's most likely a cross coupled LC oscillator. Part of the PLL used to generate the RF.The variable capacitors will be varicap diodes, used to tune it.https://smartech.gatech.edu/bitstream/handle/1853/4887/yoon_sangwoong_200412_phd.pdfhttps://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwikq_nAsYbLAhUBgBoKHWoDCz4Q5TUICQ&url=http%3A%2F%2Fwww.jsts.org%2Fhtml%2Fjournal%2Fjournal_files%2F2008%2F12%2Fyear2008volume08_04_04.pdf&psig=AFQjCNFimgLZyE9mATtjTeoQyWd3il9gow&ust=1456059193599023At microwave frequencies, it becomes feasible to have on chip inductors, but they still take up a fair amount of die space.

author: ogden
author_rank: Super Contributor
timestamp: February 25, 2016, 01:57:48 pm
content: Quote from: JJalling on February 20, 2016, 08:26:52 amDon't forget to test transmisison range for whole voltage range too - because RF TX power goes down with voltage.

author: batteksystem
author_rank: Regular Contributor
timestamp: February 26, 2016, 01:45:49 pm
content: You can consider adding a boost converter to provide enough voltage even for a coin cell.