Meanwhile, I got a reply from the 'support@m5stack.com'

they provided another solution.....

in the M5stack core2 library (~/Arduino/libraries/M5Core2/src),
in the class 'void M5Core2::begin'
change
' // I2C init
if (I2CEnable == true) {
Wire.begin(32, 33);
}'

to
' // I2C init
if (I2CEnable == true) {
Wire.begin(21, 22, 100000UL);
}'
then in the arduino code:
add 'Wire.begin(22, 21);'

then the core2 and 12-channel servo will work properly.

but the weird thing is that they still work even when I delete the line 'Wire.begin(21,22);' meaning delete all the 'Wire.begin(..,..);' in the void setup() .

this is a bit funny.

cool. I am happy to hear you got it working. Thank you for reporting back.

Thanks
Felix

Wire.begin() used to always initialize an I2C master, but in recent ESP32 Arduino framework versions an ESP32 can also be setup as I2C slave. But instead of creating a new function like Wire.beginSlave() it has been decided to overload the already existing begin() function so it can be used to initialize an I2C master or a slave.

The compiler / linker decides from the argument types which begin function to call. The I2C master begin function is defined like this:

bool begin(int sda, int scl, uint32_t frequency=0);

And the I2C slave begin function is defined like this:

bool begin(uint8_t slaveAddr, int sda, int scl, uint32_t frequency);

Now if you call Wire.begin(SDA, SCK) and SDA and SCK are defined as uint8_t the I2C slave begin is called (instead of the intended I2C master begin) since the argument types match better.

Thanks
Felix

P.S.: my original advise to typecast the arguments to (int) was useless as numbers are already defined as int.

please try this - leave Wire.begin() as it is but replace Wire with Wire1 in the two functions Servo_write_us90() and Servo_write_angle().

Explanation: M5Core2 uses Wire1 for the internal I2C and Wire for the external I2C (Groove port). Wire1 is initialized in M5.begin() and used for the touch screen.

Thanks
Felix

thanks a lot, but I still can not fix the problem, now I change to use another controller instead of core2.

my suggestion is based on other examples using I2C where the original code would initialize an I2C slave instead of an I2C master due to some recent changes in the ESP32 Arduino framework.

I am sorry, but I don't have working code to share as I don't have the necessary hardware to test (e.g. I don't have a Servo module). Sorry.

Thanks
Felix

I changed the code as you suggested, but the servo still doesn't work.

could you please share the code which works well on your side?

thanks again.

try changing this line:

Wire.begin(32, 33, 100000UL);

to:

Wire.begin((int) 32, (int) 33, 100000UL);

Thanks
Felix