define printf_P as Serial.printf on ESP32/8266 and RP2040 (arduino-pico) cores

[2bndy5]

In researching how to test #864 (because I needed to call printDetails()) I found a solution to work well with the following Arduino cores

• ESP8266
• ESP32
• arduino-pico (by earl philhower)

All of those cores have Serial.printf() defined using vsnprintf() (similar to the adafruit/arduinocore-samd). However, the ESP32 core has printf_P already defined in the extensa toolchain. So, I'm proposing

--- a/RF24_config.h
+++ b/RF24_config.h
@@ -159,12 +159,18 @@ extern HardwareSPI SPI;
     #endif // defined (__ARDUINO_X86__)
 
     // Progmem is Arduino-specific
-    #if defined(ARDUINO_ARCH_ESP8266) || defined(ESP32)
+    #if defined(ARDUINO_ARCH_ESP8266) || defined(ESP32) || (defined(ARDUINO_ARCH_RP2040) && !defined(ARDUINO_ARCH_MBED))
         #include <pgmspace.h>
         #define PRIPSTR "%s"
         #ifndef pgm_read_ptr
             #define pgm_read_ptr(p) (*(void* const*)(p))
         #endif
+        // Serial.printf() is no longer defined in the unifying Arduino/ArduinoCore-API repo
+        // Serial.printf() is defined if using the arduino-pico/esp32/8266 repo
+        #if defined(ARDUINO_ARCH_ESP32) // do not `undef` when using the espressif SDK only
+            #undef printf_P             // needed for ESP32 core
+        #endif
+        #define printf_P Serial.printf
     #elif defined(ARDUINO) && !defined(ESP_PLATFORM) && !defined(__arm__) && !defined(__ARDUINO_X86__) || defined(XMEGA)
         #include <avr/pgmspace.h>
         #define PRIPSTR "%S"

I already tested these changes on my QtPy boards using either ESP32-S2 or RP2040

Additional context

• #undef printf_P

  I'm not sure if this lib works as is in the espressif SDK for the ESP32, but I wanted to make sure that we only #undef printf_P when using the ESP32 Arduino core only.

• defined(ARDUINO_ARCH_RP2040) && !defined(ARDUINO_ARCH_MBED)

  Because the arduino cores that wrap mbed framework may not actually define Serial.printf(), I wanted to make sure that the definition of printf_P only applied to the arduino-pico core, a very popular RP2040 core that supports all boards that the PicoSDK supports and additionally multi-core processing and the PicoSDK's assembly routines feature...

[2bndy5]

I looked into the ESP32 core to see if/where printf_P was used, and it looks like it isn't used anywhere (by the core at least).

I'm not sure if #undef printf_P may cause conflicts in user apps, but I think it is safe to redefine printf_P (for now). There's nothing stopping the user code from redefining printf_P the same way that this proposal does.