Problems with hardware midi callbacks on Pico RP2040

[crashhelmets]

Hello!

I am attempting to build a Midi Controller type device with both USB and Hardware midi ports, using a Raspberry Pi Pico (RP2040). This is the first time I have used this library, so am still quite unfamiliar.

I have hardware 5pin DIN midi in and out circuitry connected to pins 0 and 1 (uart0).

If I run this sketch it seems to work fine, midi notes and midi sysex messages via the USB midi all come up in the serial monitor as expected.
https://tttapa.github.io/Control-Surface-doc/Doxygen/d0/d32/MIDI-Input-Callback_8ino-example.html#a21

however if I change the 2nd line:
USBMIDI_Interface midi;
to be hardware midi instead of USB midi:
HardwareSerialMIDI_Interface midi {Serial1, MIDI_BAUD};

all midi data on the hardware ports do post messages in the serial monitor, but they all come through as real time messages no matter what midi I send to the hardware input:
"Real-time message: ff on cable 1"

Ive tried various other Control-Surface examples and the hardware midi usually sends midi correctly, but I'm finding the receiving midi callbacks either dont work at all, or come through as the wrong message type.

Any suggestions?
Thanks!

[tttapa]

I'm unable to reproduce the issue on my end. Messages with a value of 0xFF (all ones) may indicate a hardware problem.

Here's what I tried (using the current main version of Control Surface):
I connected two Pi Picos together using their UARTs (pins 0 and 1). I uploaded a USB MIDI to Serial MIDI bridge to the first one:

#include <Control_Surface.h>
 
USBMIDI_Interface midi_usb;
HardwareSerialMIDI_Interface midi_ser{ Serial1, MIDI_BAUD };
BidirectionalMIDI_Pipe pipes;
 
void setup() {
    midi_ser | pipes | midi_usb;
    MIDI_Interface::beginAll();
}
 
void loop() {
    MIDI_Interface::updateAll();
}

Then I uploaded the MIDI-Input-Callback.ino example with the change you described to the second Pico:

#include <Control_Surface.h>  // Include the Control Surface library

HardwareSerialMIDI_Interface midi{ Serial1, MIDI_BAUD };

bool channelMessageCallback(ChannelMessage cm) {
  Serial << F("Channel message: ") << hex                    //
         << cm.header << ' ' << cm.data1 << ' ' << cm.data2  //
         << dec << F(" on cable ") << cm.cable.getOneBased() << endl;
  return true;  // Return true to indicate that handling is done,
                // and Control_Surface shouldn't handle it anymore.
                // If you want Control_Surface to handle it as well,
                // return false.
}

bool sysExMessageCallback(SysExMessage se) {
  Serial << F("System Exclusive message: [") << se.length << "] "  //
         << AH::HexDump(se.data, se.length)                        //
         << F(" on cable ") << se.cable.getOneBased() << endl;
  return true;  // Return true to indicate that handling is done,
                // and Control_Surface shouldn't handle it anymore.
                // If you want Control_Surface to handle it as well,
                // return false.
}

bool sysCommonMessageCallback(SysCommonMessage sc) {
  Serial << F("System Common message: ") << hex              //
         << sc.header << ' ' << sc.data1 << ' ' << sc.data2  //
         << dec << F(" on cable ") << sc.cable.getOneBased() << endl;
  return true;  // Return true to indicate that handling is done,
                // and Control_Surface shouldn't handle it anymore.
                // If you want Control_Surface to handle it as well,
                // return false.
}

bool realTimeMessageCallback(RealTimeMessage rt) {
  Serial << F("Real-time message: ")  //
         << hex << rt.message << dec  //
         << F(" on cable ") << rt.cable.getOneBased() << endl;
  return true;  // Return true to indicate that handling is done,
                // and Control_Surface shouldn't handle it anymore.
                // If you want Control_Surface to handle it as well,
                // return false.
}

void setup() {
  Serial.begin(115200);
  Control_Surface.begin();
  Control_Surface.setMIDIInputCallbacks(channelMessageCallback,    //
                                        sysExMessageCallback,      //
                                        sysCommonMessageCallback,  //
                                        realTimeMessageCallback);  //
  // If you don't need all four callbacks, you can pass `nullptr` instead of a
  // function pointer
}

void loop() {
  Control_Surface.loop();
}

When I send a MIDI message to the first Pico (I used amidi here, but you can use any tool that sends MIDI over USB):

amidi -p hw:1,0,0 -S "90 3C 7F"

I get the expected response from the second Pico in the serial monitor:

Channel message: 90 3c 7f on cable 1

---

To verify that you're getting meaningful data from the serial port, you can start with a minimal debugging sketch like this one:

void setup() {
  Serial.begin(115200);
  Serial1.begin(31250);
}
void loop() {
  if (Serial1.available() > 0)
    Serial.println(Serial1.read(), HEX);
}

Keep in mind that the Pi Pico is a 3.3V device. Many MIDI circuits you'll find online are designed for 5V.

[crashhelmets]

Thanks for the astonishingly fast and detailed reply. I got it working!

I assumed the midi circuit was working properly, as I was getting a response to the midi input. Also I have used the circuit (unchanged) successfully on 2 Teensys. But you were right to question it. Your serial test was just giving me FF every time, so that proved the issue was in hardware.

Turns out I had connected up the 0v wire on the midi circuit to the wrong pin on the pico! (the one next to GND). My stupid mistake.
Thanks again for the help!