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