refactor(examples/console): Warn if secondary console is active

Having a secondary serial console is not useful when applications
use a REPL console type, hence we warn for it in examples.

Closes https://github.com/espressif/esp-idf/issues/11731

examples/system/console/basic/README.md

@@ -21,6 +21,8 @@ When UART interface is used, this example should run on any commonly available E
 
 ### Using with USB_SERIAL_JTAG
 
+*NOTE: We recommend to disable the secondary console output on chips with USB_SERIAL_JTAG since the secondary serial is output-only and would not be very useful when using a console application. This is why the secondary console output is deactivated per default (CONFIG_ESP_CONSOLE_SECONDARY_NONE=y)*
+
 On chips with USB_SERIAL_JTAG peripheral, console example can be used over the USB serial port.
 
 * First, connect the USB cable to the USB_SERIAL_JTAG interface.

examples/system/console/basic/main/console_example_main.c

@@ -20,6 +20,17 @@
 #include "cmd_wifi.h"
 #include "cmd_nvs.h"
 
+/*
+ * We warn if a secondary serial console is enabled. A secondary serial console is always output-only and
+ * hence not very useful for interactive console applications. If you encounter this warning, consider disabling
+ * the secondary serial console in menuconfig unless you know what you are doing.
+ */
+#if SOC_USB_SERIAL_JTAG_SUPPORTED
+#if !CONFIG_ESP_CONSOLE_SECONDARY_NONE
+#warning "A secondary serial console is not useful when using the console component. Please disable it in menuconfig."
+#endif
+#endif
+
 static const char* TAG = "example";
 #define PROMPT_STR CONFIG_IDF_TARGET
 

examples/system/console/basic/sdkconfig.defaults

@@ -15,3 +15,6 @@ CONFIG_FREERTOS_USE_TRACE_FACILITY=y
 CONFIG_FREERTOS_USE_STATS_FORMATTING_FUNCTIONS=y
 
 CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y
+
+# On chips with USB serial, disable secondary console which does not make sense when using console component
+CONFIG_ESP_CONSOLE_SECONDARY_NONE=y