Raspberry Pi Pico target (with sparkfun lora hat) does compile but needs further work.

Also contains a small fix to make PRIVATE_HW targets build again for nRF52 architectures

variants/pico/platformio.ini

@@ -0,0 +1,17 @@
+[env:pico]
+extends = rp2040_base
+board = pico
+upload_protocol = picotool
+
+# add our variants files to the include and src paths
+build_flags = ${rp2040_base.build_flags} 
+  -DPRIVATE_HW
+  -Ivariants/pico
+  -DARDUINO_AVR_NANO_EVERY
+  -DDEBUG_RP2040_WIRE
+  -DDEBUG_RP2040_SPI
+  -DDEBUG_RP2040_CORE
+  -DDEBUG_RP2040_PORT=Serial
+  -DUSE_TINYUSB
+lib_deps =
+  ${rp2040_base.lib_deps}

variants/pico/variant.h

@@ -0,0 +1,52 @@
+// #define RADIOLIB_CUSTOM_ARDUINO 1
+// #define RADIOLIB_TONE_UNSUPPORTED 1
+// #define RADIOLIB_SOFTWARE_SERIAL_UNSUPPORTED 1
+
+#define ARDUINO_ARCH_AVR
+
+#define CBC 0
+#define CTR 1
+#define ECB 0
+
+#define NO_GPS 1
+#define USE_SH1106 1
+#undef GPS_SERIAL_NUM
+
+// #define I2C_SDA 6
+// #define I2C_SCL 7
+
+#define BUTTON_PIN 17
+#define EXT_NOTIFY_OUT 4
+
+#define BATTERY_PIN 26
+// ratio of voltage divider = 3.0 (R17=200k, R18=100k)
+#define ADC_MULTIPLIER 3.1 // 3.0 + a bit for being optimistic
+
+#define USE_RF95
+#define USE_SX1262
+
+#undef RF95_SCK
+#undef RF95_MISO
+#undef RF95_MOSI
+#undef RF95_NSS
+
+#define RF95_SCK 10
+#define RF95_MISO 12
+#define RF95_MOSI 11
+#define RF95_NSS 3
+
+#define LORA_DIO0 RADIOLIB_NC
+#define LORA_RESET 15
+#define LORA_DIO1 20
+#define LORA_DIO2 2
+#define LORA_DIO3 RADIOLIB_NC
+
+#ifdef USE_SX1262
+#define SX126X_CS RF95_NSS
+#define SX126X_DIO1 LORA_DIO1
+#define SX126X_BUSY LORA_DIO2
+#define SX126X_RESET LORA_RESET
+#define SX126X_E22
+#endif
+
+#include <Adafruit_TinyUSB.h>

variants/t-echo/platformio.ini

@@ -3,7 +3,7 @@
 extends = nrf52840_base
 board = t-echo
 debug_tool = jlink
-upload_protocol = jlink
+upload_protocol = nrfutil
 # add our variants files to the include and src paths
 # define build flags for the TFT_eSPI library - NOTE: WE NOT LONGER USE TFT_eSPI, it was for an earlier version of the TTGO eink screens
 # -DBUSY_PIN=3 -DRST_PIN=2 -DDC_PIN=28 -DCS_PIN=30