M5Stack + NRF24 = LCD slow down

jpbbricole

Hi!
I'm using a M5Stack Gray, with a NRF24L01 radio transmitter.

#include <M5Stack.h>
#include <RF24.h>

//------------------------------------- Radio RF24
#define rf24CePin 16
#define rf24CsnPin 17

RF24 RF24(rf24CePin, rf24CsnPin);

As soon as I invoke a RF24 function like RF24.available() or RF24.printDetails(), the LCD display of the M5Stack slows down dramatically.
At the start, the SPI BUS of the M5Stak is at 40mHz (In_eSPI_Setup.h #define SPI_FREQUENCY 40000000 // Maximum to use SPIFFS), it seems to me that it falls below 1mHz.
Why?

Thanks for your help

cordially
jpbbricole

jpbbricole

Hi
I found the reason for the slowdown of the LCD display, it's in RF24-master library, file RF24.cpp.

            #elif F_CPU < 320000000
            _SPI.setClockDivider(SPI_CLOCK_DIV32);

As the speed of the M5Stack is 24000000, that divided the frequency of the SPI by 32.
I added

             #elif F_CPU == 240000000                     // For M5Stack Grey
            _SPI.setClockDivider(SPI_CLOCK_DIV2);                // For M5Stack Grey

and the problem is solved.

Thanks for reading me

cordially
jpbbricole

world101

Glad you found the issue. I’m interested in seeing your full code once you have it done. I’m also interested in using the NRF24L01 in a project idea that I have been thinking of.

jpbbricole

Hi world101

To make this modification, I determined the speed of the M5Stack by making a program with:

Serial.println (F_CPU)

which gave 24000000

Then, I modified the file ..\libraries\RF24-master\RF24.cpp by adding these lines (who have // For M5Stack Gray as a remark)

#if !defined(SOFTSPI)
    _SPI.setBitOrder(MSBFIRST);
    _SPI.setDataMode(SPI_MODE0);
            #if !defined(F_CPU) || F_CPU < 20000000
        _SPI.setClockDivider(SPI_CLOCK_DIV2);
                #elif F_CPU < 40000000
        _SPI.setClockDivider(SPI_CLOCK_DIV4);
                #elif F_CPU < 80000000
        _SPI.setClockDivider(SPI_CLOCK_DIV8);
                #elif F_CPU < 160000000
        _SPI.setClockDivider(SPI_CLOCK_DIV16);
               #elif F_CPU == 240000000                      // For M5Stack Grey
        _SPI.setClockDivider(SPI_CLOCK_DIV2);                // For M5Stack Grey**
                #elif F_CPU < 320000000
        _SPI.setClockDivider(SPI_CLOCK_DIV32);
                #elif F_CPU < 640000000
        _SPI.setClockDivider(SPI_CLOCK_DIV64);
                #elif F_CPU < 1280000000
        _SPI.setClockDivider(SPI_CLOCK_DIV128);
                #else
                    #error "Unsupported CPU frequency. Please set correct SPI divider."
                #endif

            #endif

Regarding the program where I use the RF24, it is very large, I can, if you want, give you an example of use, with several pipes.

cordially
jpbbricole