Raspberry pi pico unable to use 2 hardware serial ports (Serial1&2)

[MNS26]

I was redirected here form platfromIO to open an issue about it.
( platformio/platform-raspberrypi#3 )

I've been trying it read my gps module for a project and decided to use the pi pico for it, however even though it "sees" the connection (no check wire connection message) it receives no data.

i used the default "FullExampel" file from the TinyGPS library
i removed SoftwareSerial because there is no interrup.h file and replaced it with Serial1 (RP pi pico should be able to have 2 hardware serial connections)

GPS lock is established (red led)

data from serial console

[Gerriko]

I've tested this using a standard Raspberry Pi Pico board and I was able to get the Pico to use a 2nd serial port (as well as still use USB/CDC Virtual Serial), but it requires modifying ArduinoCore-mbed code.

However, I think that this mod requires plenty of testing as on my first few tests it appears unstable. When I reset my board using my own reset button I get an mbed error on the Serial1 port only. But then this error clears on 2nd reset and my test sketch works. The error only happens with a manual reset otherwise my mod appears to work.

++ MbedOS Error Info ++
Error Status: 0x80010133 Code: 307 Module: 1
Error Message: Mutex: 0x2000C274, Not allowed in ISR context
Location: 0x10004007
Error Value: 0x2000C274
Current Thread: rtx_idle Id: 0x2000CE30 Entry: 0x10004011 StackSize: 0x200 StackMem: 0x2000B9B8 SP: 0x2003FD14 
For more info, visit: https://mbed.com/s/error?error=0x80010133&osver=61000&core=0x410CC601&comp=2&ver=100300&tgt=RASPBERRY_PI...

-- MbedOS Error Info --

So what did I do...
First, you need to open up pin_arduino.h found in the variants/RASPBERRY_PI_PICO folder:
https://github.com/arduino/ArduinoCore-mbed/blob/master/variants/RASPBERRY_PI_PICO/pins_arduino.h

Then for my Serial pins I used the following (I believe you are quite limited on choice of pins to prevent clashing with SPI/I2C):

// Serial
#define PIN_SERIAL_TX (0ul)
#define PIN_SERIAL_RX (1ul)
#define PIN_SERIAL_TX2 (8ul)
#define PIN_SERIAL_RX2 (9ul)

Then you add in some new additions. First increase SERIAL_HOWMANY to 2 and then add in SERIAL2 TX/RX

#define SERIAL_HOWMANY		2
#define SERIAL1_TX			(digitalPinToPinName(PIN_SERIAL_TX))
#define SERIAL1_RX			(digitalPinToPinName(PIN_SERIAL_RX))
#define SERIAL2_TX			(digitalPinToPinName(PIN_SERIAL_TX2))
#define SERIAL2_RX			(digitalPinToPinName(PIN_SERIAL_RX2))

And that is all I did.

I was not sure about this code though and what it was doing internally:

#define SERIAL_PORT_HARDWARE        Serial1
#define SERIAL_PORT_HARDWARE_OPEN   Serial1

Then for my Arduino sketch, I simply modified the existing SerialPassthrough sketch as follows:

void setup() {
  Serial.begin(115200);
  Serial1.begin(115200);
  Serial2.begin(115200);

  delay(100);
  Serial.println("Lets start");
  // Just a quick initial test to make sure I am seeing text in both my serial terminals
  for (auto i = 0; i < 6; i++) {
    delay(3000);
    Serial1.println("Hello world 1");  
    Serial2.println("Hello world 2");
  }
  Serial.println("We are finished first test");
}

void loop() {
  if (Serial2.available()) {      // If anything comes in Serial (USB),
    Serial1.write(Serial2.read());   // read it and send it out Serial1 (pins 0 & 1)
    Serial.print(".");          // output via usb just in case we don't get anything
  }

  if (Serial1.available()) {     // If anything comes in Serial1 (pins 0 & 1)
    Serial2.write(Serial1.read());   // read it and send it out Serial (USB)
    Serial.print(".");          // output via usb just in case we don't get anything
  }
}

[facchinm]

Hi @MNS26 and @Gerriko ,
I just posted a PR #240 to ease the creation of additional serial objects without touching the core.
By applying it the resulting sketch will look like

UART Serial2(8,9);

void setup() {
  Serial.begin(115200);
  Serial1.begin(115200);
  Serial2.begin(115200);

  delay(100);
  Serial.println("Lets start");
  // Just a quick initial test to make sure I am seeing text in both my serial terminals
  for (auto i = 0; i < 6; i++) {
    delay(3000);
    Serial1.println("Hello world 1");  
    Serial2.println("Hello world 2");
  }
  Serial.println("We are finished first test");
}

void loop() {
  if (Serial2.available()) {      // If anything comes in Serial (USB),
    Serial1.write(Serial2.read());   // read it and send it out Serial1 (pins 0 & 1)
    Serial.print(".");          // output via usb just in case we don't get anything
  }

  if (Serial1.available()) {     // If anything comes in Serial1 (pins 0 & 1)
    Serial2.write(Serial1.read());   // read it and send it out Serial (USB)
    Serial.print(".");          // output via usb just in case we don't get anything
  }
}

I tested it on a Pico and couldn't reproduce the crash that @Gerriko is reporting. Could you test if the issue is reproducible after the PR is applied? Thx

[MNS26]

Hi @MNS26 and @Gerriko ,
I just posted a PR #240 to ease the creation of additiona serial objects without touching the core.
By apply it the resulting sketch will look like

UART Serial2(8,9);

void setup() {
  Serial.begin(115200);
  Serial1.begin(115200);
  Serial2.begin(115200);

  delay(100);
  Serial.println("Lets start");
  // Just a quick initial test to make sure I am seeing text in both my serial terminals
  for (auto i = 0; i < 6; i++) {
    delay(3000);
    Serial1.println("Hello world 1");  
    Serial2.println("Hello world 2");
  }
  Serial.println("We are finished first test");
}

void loop() {
  if (Serial2.available()) {      // If anything comes in Serial (USB),
    Serial1.write(Serial2.read());   // read it and send it out Serial1 (pins 0 & 1)
    Serial.print(".");          // output via usb just in case we don't get anything
  }

  if (Serial1.available()) {     // If anything comes in Serial1 (pins 0 & 1)
    Serial2.write(Serial1.read());   // read it and send it out Serial (USB)
    Serial.print(".");          // output via usb just in case we don't get anything
  }
}

I tested it on a Pico and couldn't reproduce the crash that @Gerriko is reporting. Could you test if the issue is reproducible after the PR is applied? Thx

@facchinm after i edited the pins_arduino.h file and tried to use your example i cant get it to compile, everytime i try to do it i get this

> Executing task: C:\Users\MS26\.platformio\penv\Scripts\platformio.exe run --environment pico helicopter <

Processing pico helicopter (platform: https://github.com/platformio/platform-raspberrypi.git; framework: arduino; board: pico)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Verbose mode can be enabled via `-v, --verbose` option
CONFIGURATION: https://docs.platformio.org/page/boards/raspberrypi/pico.html
PLATFORM: Raspberry Pi RP2040 (1.0.0+sha.095da74) > Raspberry Pi Pico
HARDWARE: RP2040 133MHz, 264KB RAM, 2MB Flash
DEBUG: Current (cmsis-dap) External (cmsis-dap, jlink, raspberrypi-swd)
PACKAGES:
 - framework-arduino-mbed 2.1.0
 - tool-rp2040tools 1.0.2
 - toolchain-gccarmnoneeabi 1.90201.191206 (9.2.1)
LDF: Library Dependency Finder -> http://bit.ly/configure-pio-ldf
LDF Modes: Finder ~ chain, Compatibility ~ soft
Found 31 compatible libraries
Scanning dependencies...
Dependency Graph
|-- <Wire>
|-- <TinyGPSPlus> 1.0.2
Building in release mode
Compiling .pio\build\pico helicopter\src\main.cpp.o
Compiling .pio\build\pico helicopter\src\main1.cpp.o
Compiling .pio\build\pico helicopter\lib1b0\Wire\Wire.cpp.o
Compiling .pio\build\pico helicopter\libf0e\TinyGPSPlus\TinyGPS++.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduinoVariant\double_tap_usb_boot.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduinoVariant\variant.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\Interrupts.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\Serial.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\Tone.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\USB\PluggableUSBDevice.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\USB\USBCDC.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\USB\USBSerial.cpp.o
In file included from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/platform_defs.h:12,
                 from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/pico_platform/include/pico/platform.h:12,
                 from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/common/pico_base/include/pico.h:19,
                 from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\variants\RASPBERRY_PI_PICO\double_tap_usb_boot.cpp:2:
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h: In function 'uint32_t time_us_32()':       
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/regs/addressmap.h:56:20: warning: type qualifiers ignored on cast result type [-Wignored-qualifiers]
   56 | #define TIMER_BASE 0x40054000
      |                    ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_structs/include/hardware/structs/timer.h:33:38: note: in expansion of macro 'TIMER_BASE'
   33 | #define timer_hw ((timer_hw_t *const)TIMER_BASE)
      |                                      ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h:66:12: note: in expansion of macro 'timer_hw'
   66 |     return timer_hw->timerawl;
      |            ^~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h: In function 'bool time_reached(absolute_time_t)':
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/regs/addressmap.h:56:20: warning: type qualifiers ignored on cast result type [-Wignored-qualifiers]
   56 | #define TIMER_BASE 0x40054000
      |                    ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_structs/include/hardware/structs/timer.h:33:38: note: in expansion of macro 'TIMER_BASE'
   33 | #define timer_hw ((timer_hw_t *const)TIMER_BASE)
      |                                      ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h:110:19: note: in expansion of macro 'timer_hw'
  110 |     uint32_t hi = timer_hw->timerawh;
      |                   ^~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/regs/addressmap.h:56:20: warning: type qualifiers ignored on cast result type [-Wignored-qualifiers]
   56 | #define TIMER_BASE 0x40054000
      |                    ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_structs/include/hardware/structs/timer.h:33:38: note: in expansion of macro 'TIMER_BASE'
   33 | #define timer_hw ((timer_hw_t *const)TIMER_BASE)
      |                                      ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h:111:33: note: in expansion of macro 'timer_hw'
  111 |     return (hi >= hi_target && (timer_hw->timerawl >= (uint32_t) target || hi != hi_target));
      |                                 ^~~~~~~~
src\main1.cpp:16: warning: "PIN_SERIAL_TX" redefined
   16 | #define PIN_SERIAL_TX (4)
      |
In file included from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Arduino.h:79,
                 from src\main1.cpp:1:
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\variants\RASPBERRY_PI_PICO/pins_arduino.h:41: note: this is the location of the previous definition
   41 | #define PIN_SERIAL_TX (0ul)
      |
src\main1.cpp:17: warning: "PIN_SERIAL_RX" redefined
   17 | #define PIN_SERIAL_RX (5)
      |
In file included from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Arduino.h:79,
                 from src\main1.cpp:1:
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\variants\RASPBERRY_PI_PICO/pins_arduino.h:42: note: this is the location of the previous definition
   42 | #define PIN_SERIAL_RX (1ul)
      |
src\main.cpp:3:17: error: no matching function for call to 'arduino::UART::UART(int, int)'
    3 | UART Serial2(4,5);
      |                 ^
In file included from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Arduino.h:105,
                 from src\main.cpp:1:
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:42:3: note: candidate: 'arduino::UART::UART()'
   42 |   UART() {
      |   ^~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:42:3: note:   candidate expects 0 arguments, 2 provided
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:41:3: note: candidate: 'arduino::UART::UART(int, int, int, int)'
   41 |   UART(int tx, int rx, int rts, int cts) : _tx((PinName)tx), _rx((PinName)rx), _rts((PinName)rts), _cts((PinName)cts) {}
      |   ^~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:41:3: note:   candidate expects 4 arguments, 2 provided
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note: candidate: 'constexpr arduino::UART::UART(const arduino::UART&)'
   39 | class UART : public HardwareSerial {
      |       ^~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note:   candidate expects 1 argument, 2 provided
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note: candidate: 'constexpr arduino::UART::UART(arduino::UART&&)'
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note:   candidate expects 1 argument, 2 provided
.pio\libdeps\pico helicopter\TinyGPSPlus\src\TinyGPS++.cpp: In member function 'bool TinyGPSPlus::encode(char)':
.pio\libdeps\pico helicopter\TinyGPSPlus\src\TinyGPS++.cpp:63:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
   63 |     parity ^= (uint8_t)c;
      |     ~~~~~~~^~~~~~~~~~~~~
.pio\libdeps\pico helicopter\TinyGPSPlus\src\TinyGPS++.cpp:64:3: note: here
   64 |   case '\r':
      |   ^~~~
*** [.pio\build\pico helicopter\src\main.cpp.o] Error 1
================================================================================================ [FAILED] Took 16.64 seconds ================================================================================================
The terminal process "C:\Users\MS26\.platformio\penv\Scripts\platformio.exe 'run', '--environment', 'pico helicopter'" terminated with exit code: 1.

Terminal will be reused by tasks, press any key to close it.

and the code i used

#include <Arduino.h>

UART Serial2(4,5);

void setup() {
  Serial.begin(115200);
  Serial1.begin(115200);
  Serial2.begin(115200);

  delay(100);
  Serial.println("Lets start");
  // Just a quick initial test to make sure I am seeing text in both my serial terminals
  for (auto i = 0; i < 6; i++) {
    delay(3000);
    Serial1.println("Hello world 1");  
    Serial2.println("Hello world 2");
  }
  Serial.println("We are finished first test");
}

void loop() {
  if (Serial2.available()) {      // If anything comes in Serial (USB),
    Serial.write(Serial2.read());   // read it and send it out Serial1 (pins 0 & 1)
    Serial.println();          // output via usb just in case we don't get anything
  }
/*
  if (Serial1.available()) {     // If anything comes in Serial1 (pins 0 & 1)
    Serial2.write(Serial1.read());   // read it and send it out Serial (USB)
    Serial.print(".");          // output via usb just in case we don't get anything
  }*/
}

[Gerriko]

@MNS26 you say " i edited the pins_arduino.h file "

When looking through the error log it tells you "warning: "PIN_SERIAL_TX" redefined" and "warning: "PIN_SERIAL_RX" redefined".

That suggests to me that Serial2 and Serial1 and trying to use the same PIN_SERIAL_TX and PIN_SERIAL_RX.

Maybe check your pins_arduino.h file again.

[MNS26]

@Gerriko I have pin GP4 and pin GP5 for serial 1 (GPS) and plan on using GP12 and GP13 for serial 0 (RC receiver).
In the pins_arduino.h file
pin definition

// Serial
#define PIN_SERIAL_TX (0ul)
#define PIN_SERIAL_RX (1ul)

#define PIN_SERIAL_TX2 (8ul)
#define PIN_SERIAL_RX2 (9ul)

serialX definition

//SERIAL Setup
#define SERIAL_HOWMANY		2
#define SERIAL1_TX			(digitalPinToPinName(PIN_SERIAL_TX))
#define SERIAL1_RX			(digitalPinToPinName(PIN_SERIAL_RX))

#define SERIAL2_TX			(digitalPinToPinName(PIN_SERIAL_TX2))
#define SERIAL2_RX			(digitalPinToPinName(PIN_SERIAL_RX2))

i used GP0 and GP1 for a I2C sensor (mpu6050 with auxiliary I2C enabled for compass).

EDIT:
Found the redefine issue (a file i forgot to remove in the project folder).
but now the output changed to

> Executing task: C:\Users\MS26\.platformio\penv\Scripts\platformio.exe run --environment pico helicopter <

Processing pico helicopter (platform: https://github.com/platformio/platform-raspberrypi.git; framework: arduino; board: pico)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Verbose mode can be enabled via `-v, --verbose` option
CONFIGURATION: https://docs.platformio.org/page/boards/raspberrypi/pico.html
PLATFORM: Raspberry Pi RP2040 (1.0.0+sha.095da74) > Raspberry Pi Pico
HARDWARE: RP2040 133MHz, 264KB RAM, 2MB Flash
DEBUG: Current (cmsis-dap) External (cmsis-dap, jlink, raspberrypi-swd)
PACKAGES:
 - framework-arduino-mbed 2.1.0
 - tool-rp2040tools 1.0.2
 - toolchain-gccarmnoneeabi 1.90201.191206 (9.2.1)
LDF: Library Dependency Finder -> http://bit.ly/configure-pio-ldf
LDF Modes: Finder ~ chain, Compatibility ~ soft
Found 31 compatible libraries
Scanning dependencies...
No dependencies
Building in release mode
Compiling .pio\build\pico helicopter\src\main.cpp.o
Archiving .pio\build\pico helicopter\libFrameworkArduinoVariant.a
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_analog.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_digital.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_pulse.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_shift.cpp.o
src\main.cpp:3:17: error: no matching function for call to 'arduino::UART::UART(int, int)'
    3 | UART Serial2(4,5);
      |                 ^
In file included from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Arduino.h:105,
                 from src\main.cpp:1:
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:42:3: note: candidate: 'arduino::UART::UART()'
   42 |   UART() {
      |   ^~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:42:3: note:   candidate expects 0 arguments, 2 provided
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:41:3: note: candidate: 'arduino::UART::UART(int, int, int, int)'
   41 |   UART(int tx, int rx, int rts, int cts) : _tx((PinName)tx), _rx((PinName)rx), _rts((PinName)rts), _cts((PinName)cts) {}
      |   ^~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:41:3: note:   candidate expects 4 arguments, 2 provided
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note: candidate: 'constexpr arduino::UART::UART(const arduino::UART&)'
   39 | class UART : public HardwareSerial {
      |       ^~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note:   candidate expects 1 argument, 2 provided
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note: candidate: 'constexpr arduino::UART::UART(arduino::UART&&)'
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/Serial.h:39:7: note:   candidate expects 1 argument, 2 provided
*** [.pio\build\pico helicopter\src\main.cpp.o] Error 1
==================================================================================================== [FAILED] Took 5.55 seconds ====================================================================================================The terminal process "C:\Users\MS26\.platformio\penv\Scripts\platformio.exe 'run', '--environment', 'pico helicopter'" terminated with exit code: 1.

Terminal will be reused by tasks, press any key to close it.

But when i remove the line
UART Serial2(4,5);
will compile without any issues at all.

[MNS26]

Is there anything else i can try to get it to work?
@facchinm do you have any idea why it does compile (but not work) when removing the UART Serial2(4,5); line?
Ive been trying things out in my free time here and there but i either fail to compile it (same thing as previous message) or the serial port is not made.

Should i see this project as a lost cause and "drop it"? or is there still a light somewhere at the end of the tunnel.

[resolvethis]

The proposed code did not compile as it was shown there.

UART Serial2(8, 9); // did not compile

I got the following error:

no matching function for call to 'arduino::UART::UART(int, int)'
...
note: candidate: arduino::UART::UART(int, int, int, int)

What worked for me was:

UART Serial2(8, 9, 0, 0);

Full code:

    #include <Arduino.h>
    
    UART Serial2(8, 9, 0, 0);
    
    void setup() {
      Serial2.begin(9600);
      // ...
      Serial2.write("hello world");
    }
    
    void loop {}

[MNS26]

@resolvethis Did you also edit the pins_arduino.h file? When i try and use your code (and adding the () to loop) i still get a error.

Processing pico helicopter (platform: https://github.com/platformio/platform-raspberrypi.git; framework: arduino; board: pico)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------Verbose mode can be enabled via `-v, --verbose` option
CONFIGURATION: https://docs.platformio.org/page/boards/raspberrypi/pico.html
PLATFORM: Raspberry Pi RP2040 (1.1.0+sha.3c6cc84) > Raspberry Pi Pico
HARDWARE: RP2040 133MHz, 264KB RAM, 2MB Flash
DEBUG: Current (cmsis-dap) External (cmsis-dap, jlink, raspberrypi-swd)
PACKAGES:
 - framework-arduino-mbed 2.1.0
 - tool-rp2040tools 1.0.2
 - toolchain-gccarmnoneeabi 1.90201.191206 (9.2.1)
LDF: Library Dependency Finder -> http://bit.ly/configure-pio-ldf
LDF Modes: Finder ~ chain, Compatibility ~ soft
Found 31 compatible libraries
Scanning dependencies...
Dependency Graph
|-- <TinyGPSPlus> 1.0.2
Building in release mode
Compiling .pio\build\pico helicopter\src\main.cpp.o
Compiling .pio\build\pico helicopter\libf0e\TinyGPSPlus\TinyGPS++.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduinoVariant\double_tap_usb_boot.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduinoVariant\variant.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\Interrupts.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\Serial.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\Tone.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\USB\PluggableUSBDevice.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\USB\USBCDC.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\USB\USBSerial.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\main.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\pinToIndex.cpp.o
In file included from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/platform_defs.h:12,
                 from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/pico_platform/include/pico/platform.h:12,
                 from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/common/pico_base/include/pico.h:19,
                 from C:\Users\MS26\.platformio\packages\framework-arduino-mbed\variants\RASPBERRY_PI_PICO\double_tap_usb_boot.cpp:2:
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h: In function 'uint32_t time_us_32()':
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/regs/addressmap.h:56:20: warning: type qualifiers ignored on cast result type [-Wignored-qualifiers]
   56 | #define TIMER_BASE 0x40054000
      |                    ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_structs/include/hardware/structs/timer.h:33:38: note: in expansion of macro 'TIMER_BASE'
   33 | #define timer_hw ((timer_hw_t *const)TIMER_BASE)
      |                                      ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h:66:12: note: in expansion of macro 'timer_hw'
   66 |     return timer_hw->timerawl;
      |            ^~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h: In function 'bool time_reached(absolute_time_t)':
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/regs/addressmap.h:56:20: warning: type qualifiers ignored on cast result type [-Wignored-qualifiers]
   56 | #define TIMER_BASE 0x40054000
      |                    ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_structs/include/hardware/structs/timer.h:33:38: note: in expansion of macro 'TIMER_BASE'
   33 | #define timer_hw ((timer_hw_t *const)TIMER_BASE)
      |                                      ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h:110:19: note: in expansion of macro 'timer_hw'
  110 |     uint32_t hi = timer_hw->timerawh;
      |                   ^~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_regs/include/hardware/regs/addressmap.h:56:20: warning: type qualifiers ignored on cast result type [-Wignored-qualifiers]
   56 | #define TIMER_BASE 0x40054000
      |                    ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2040/hardware_structs/include/hardware/structs/timer.h:33:38: note: in expansion of macro 'TIMER_BASE'
   33 | #define timer_hw ((timer_hw_t *const)TIMER_BASE)
      |                                      ^~~~~~~~~~
C:\Users\MS26\.platformio\packages\framework-arduino-mbed\cores\arduino/mbed/targets/TARGET_RASPBERRYPI/TARGET_RP2040/pico-sdk/rp2_common/hardware_timer/include/hardware/timer.h:111:33: note: in expansion of macro 'timer_hw'
  111 |     return (hi >= hi_target && (timer_hw->timerawl >= (uint32_t) target || hi != hi_target));
      |                                 ^~~~~~~~
.pio\libdeps\pico helicopter\TinyGPSPlus\src\TinyGPS++.cpp: In member function 'bool TinyGPSPlus::encode(char)':
.pio\libdeps\pico helicopter\TinyGPSPlus\src\TinyGPS++.cpp:63:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
   63 |     parity ^= (uint8_t)c;
      |     ~~~~~~~^~~~~~~~~~~~~
.pio\libdeps\pico helicopter\TinyGPSPlus\src\TinyGPS++.cpp:64:3: note: here
   64 |   case '\r':
      |   ^~~~
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_analog.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_digital.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_pulse.cpp.o
Compiling .pio\build\pico helicopter\FrameworkArduino\wiring_shift.cpp.o
Archiving .pio\build\pico helicopter\libFrameworkArduino.a
Linking .pio\build\pico helicopter\firmware.elf
c:/users/ms26/.platformio/packages/toolchain-gccarmnoneeabi/bin/../lib/gcc/arm-none-eabi/9.2.1/../../../../arm-none-eabi/bin/ld.exe: .pio\build\pico helicopter\libFrameworkArduino.a(Serial.cpp.o):(.bss._UART2_+0x0): multiple definition of `_UART2_'; .pio\build\pico helicopter\src\main.cpp.o:(.bss._UART2_+0x0): first defined here  
collect2.exe: error: ld returned 1 exit status
*** [.pio\build\pico helicopter\firmware.elf] Error 1
==================================================================== [FAILED] Took 13.01 seconds ====================================================================
The terminal process "C:\Users\MS26\.platformio\penv\Scripts\platformio.exe 'run', '--environment', 'pico helicopter'" terminated with exit code: 1.

Terminal will be reused by tasks, press any key to close it.

but when i set #define SERIAL_HOWMANY to 1 it compiles without a problem.

[MNS26]

@facchinm has there been any news on this issue? I have yet to find a way to use multiple serial ports at once.

[aord]

Many thanks to those above, especially facchinm:
Below is what I used for my NEO GPS connected to the Pico.
I had trouble with Serial1, every time I used Serial1 along with Serial it would lock up the PC comport. I'm guessing that serial1 is the same as serial? I don't know, but the following code worked for me:

#include <TinyGPSPlus.h>

TinyGPSPlus gps;

// The serial connection to the GPS device
UART Serial2(8,9);
//THE GPS TX goes to GP9 to work, 9 on the PICO to the recieve pin
//THE GPS TX goes to GP9 to work, 9 on the PICO to the recieve pin

void setup()
{
Serial.begin(9600);
Serial2.begin(9600); //You might be 4800 depending on your GPS?
}

void loop()
{

delay(500);
// This sketch displays information every time a new sentence is correctly encoded.
while (Serial2.available() > 0)
{
if (gps.encode(Serial2.read()))
displayInfo();
}

if (millis() > 5000 && gps.charsProcessed() < 10)
{
Serial.println(F("No GPS detected: check wiring."));
//while(true);
delay(7000);
Serial.println("Waited 7 sec for you to wire");
}
}

void displayInfo()
{
Serial.print(F("Location: "));
if (gps.location.isValid())
{
Serial.print(gps.location.lat(), 6);
Serial.print(F(","));
Serial.print(gps.location.lng(), 6);
}
else
{
Serial.print(F("INVALID"));
}

Serial.print(F(" Date/Time: "));
if (gps.date.isValid())
{
Serial.print(gps.date.month());
Serial.print(F("/"));
Serial.print(gps.date.day());
Serial.print(F("/"));
Serial.print(gps.date.year());
}
else
{
Serial.print(F("INVALID"));
}

Serial.print(F(" "));
if (gps.time.isValid())
{
if (gps.time.hour() < 10) Serial.print(F("0"));
Serial.print(gps.time.hour());
Serial.print(F(":"));
if (gps.time.minute() < 10) Serial.print(F("0"));
Serial.print(gps.time.minute());
Serial.print(F(":"));
if (gps.time.second() < 10) Serial.print(F("0"));
Serial.print(gps.time.second());
Serial.print(F("."));
if (gps.time.centisecond() < 10) Serial.print(F("0"));
Serial.print(gps.time.centisecond());
}
else
{
Serial.print(F("INVALID"));
}

Serial.println();
}