ESP8266 Community Forum

I compiled the i2sduplex.c project from CNLohr . It’s a very nice masterpiece. THANKS!
(https://github.com/cnlohr/esp8266duplex ... 2sduplex.c)
I would like to use the 26MHz ESP8266 clock for an additional device in my test setup.
I added the command:

PIN_FUNC_SELECT(PERIPHS_IO_MUX_GPIO0_U, FUNC_CLK_OUT );

to output the clock on GPIO0. When the code runs I measure a nice 26MHz square wave on the pin.
Everything looks fine while I got problem with the behavior of the program. After a second the wifi operation crash and the WIFI led blinks with not regular timing.
I reduced the WIFI to a SOFTAP with periodic udp message. Without the output clock it’s ok. When I place the clock out wifi operation crashed not for a watch dog reset.
Then instead of CLOCK_OUT I tried FUNC_CLK_XTAL:

PIN_FUNC_SELECT(PERIPHS_IO_MUX_GPIO4_U, FUNC_CLK_XTAL);

I got the same result. GPIO04 outputs a nice 26 MHz square wave while wifi crash some second after?
I used three different module (12E,12F) with same result.
I’m a newbie.
Please advice me on the use of internal 26MHz signals. Does they interfere with the wifi?