Joy-Cons report strange sensor values when they are connected via Bluetooth

[homma]

System Information

OS: macOS Tahoe 26.0.1
CPU: Apple M2 Pro
SDL revision: SDL-3.3.3-3a59163

Issue

When Joy-Cons are connected via Bluetooth, they report strange values for SDL_SENSOR_ACCEL_L and SDL_SENSOR_ACCEL_R.

My code is like below.

    // update sensors
    SDL_UpdateGamepads();

    // get sensor data
    SDL_GetGamepadSensorData(gamepad, SDL_SENSOR_ACCEL_L, accel_l, num_data);
    SDL_GetGamepadSensorData(gamepad, SDL_SENSOR_ACCEL_R, accel_r, num_data);

    // print sensor data
    std::println("Accel [L]: {}, {}, {}", accel_l[0], accel_l[1], accel_l[2]);
    std::println("Accel [R]: {}, {}, {}", accel_r[0], accel_r[1], accel_r[2]);

The above code prints like below when Joy-Cons are connected via Bluetooth.
The Y components (gravity) are around 5 but it should be around 9.8.
Also, Z component of right Joy-Con is infinite.

// connected via Bluetooth
Accel [L]: 0.68188006, 5.286458, 3.4357657
Accel [R]: -0.11032482, 5.686278, inf

When Joy-Cons are connected via USB (using Joy-Con Charging Grip), the above code prints like below.
The Y components are around 9.8 as expected.

// connected via USB
Accel [L]: 0.19073273, 10.117623, 1.137454
Accel [R]: 0.12826635, 9.966133, 1.1899831

Please take a look at the attached bluetooth.txt for an actual log for Bluetooth connection and usb.txt for USB connection.

How to replicate the issue

I have attached a program (main.cpp) to replicate the issue.

main.cpp

bluetooth.txt

usb.txt

[homma]

I have checked the sensor values in SDL2 as well.

It seems that there were some significant changes between 2.30 and 2.32 for the right Joy-Con.

The sensor values for the right Joy-Con look good on 2.30.12.
Y value is around 9.8 as expected.

2.30.12:

Accel [L]: 0.6163386, 3.4831388, -0.08852515
Accel [R]: 0.50035757, 9.628891, -0.33277372

On the other hand, there are something wrong with the sensor values for the right Joy-Con on 2.32.11.

2.32.11:

Accel [L]: 1.998067, 5.3574085, -0.36191353
Accel [R]: -0.25987625, 5.7548733, -inf

I have attached the test code (main.cpp) and the results for both versions (2.30-bluetooth.txt, 2.32-bluetooth.txt).

main.cpp

2.30-bluetooth.txt

2.32-bluetooth.txt

[slouken]

Interesting, it's working correctly here for me. I wonder if this is a macOS specific issue?

INFO: Accel [_]: 0.030845, 9.649258, -1.322164
INFO: Accel [L]: 0.079891, 9.938074, -1.440793
INFO: Accel [R]: 0.030845, 9.649258, -1.322164

Here's the updated version for Windows:

#include "SDL.h"
#include <csignal>
#include <print>

SDL_GameController *gamepad;

int num_data = 3;
float accel[3];
float gyro[3];
float accel_l[3];
float gyro_l[3];
float accel_r[3];
float gyro_r[3];

SDL_SensorType sensors[] = {
    SDL_SENSOR_ACCEL,
    SDL_SENSOR_GYRO,
    SDL_SENSOR_ACCEL_L,
    SDL_SENSOR_GYRO_L,
    SDL_SENSOR_ACCEL_R,
    SDL_SENSOR_GYRO_R,
};

auto print_sdl_version() -> void
{
    SDL_Log("### SDL version ###");
    SDL_Log("\n");
    ;

    auto p = SDL_GetPlatform();
    SDL_Log("platform:         %s", p);

    SDL_version version;
    SDL_GetVersion(&version);
    SDL_Log("version:          %d.%d.%d", version.major, version.minor,
            version.patch);

    auto r = SDL_GetRevision();
    SDL_Log("revision:         %s", r);

    SDL_Log("\n");
    ;
}

auto print_dev_info(SDL_hid_device_info *dev_info) -> void
{
    SDL_Log("### HIDAPI device ###");
    SDL_Log("\n");
    ;

    wprintf(L"product:          %ls\n", dev_info->product_string);
    SDL_Log("vendor id:        {}", dev_info->vendor_id);
    SDL_Log("product id:       {}", dev_info->product_id);

    /*
      // SDL2 does not have bus_typ
      switch (dev_info->bus_type) {
      case SDL_HID_API_BUS_USB:
        SDL_Log("bus type:         USB");
        break;
      case SDL_HID_API_BUS_BLUETOOTH:
        SDL_Log("bus type:         BLUETOOTH");
        break;
      default:
        break;
      }
    */

    SDL_Log("\n");
    ;
}

auto print_all_dev_info() -> void
{
    auto head = SDL_hid_enumerate(0, 0);
    auto dev = head;

    while (true) {
        print_dev_info(dev);

        if (dev->next == NULL) {
            break;
        } else {
            dev = dev->next;
        }
    }

    SDL_hid_free_enumeration(head);
}

auto print_hidapi_info() -> void
{
    SDL_hid_init();

    print_all_dev_info();

    SDL_hid_exit();
}

auto find_gamepad() -> void
{

    // find Joy-Con
    auto n = SDL_NumJoysticks();
    for (int i = 0; i < n; i++) {
        if (SDL_IsGameController(i) == SDL_TRUE) {
            auto type = SDL_GameControllerTypeForIndex(i);
            if (type == SDL_CONTROLLER_TYPE_NINTENDO_SWITCH_JOYCON_PAIR) {
                gamepad = SDL_GameControllerOpen(i);
                break;
            }
        }
    }
}

auto enable_sensors() -> void
{
    for (auto t : sensors) {
        if (SDL_GameControllerHasSensor(gamepad, t)) {
            SDL_GameControllerSetSensorEnabled(gamepad, t, SDL_TRUE);
        }
    }
}

auto print_gamepad() -> void
{
    auto instance_id = SDL_GameControllerGetJoystick(gamepad);
    auto name = SDL_JoystickName(instance_id);
    if (name != NULL) {
        SDL_Log("### Joystick ###");
        SDL_Log("\n");
        ;
        SDL_Log("name:             %s", name);
        SDL_Log("\n");
        ;
    }
}

auto print_sensors() -> void
{
    SDL_Log("### Sensor data ###");
    SDL_Log("\n");
    ;

    auto count = 4;
    for (auto i = 0; i < count; i++) {

        // update sensors
        SDL_GameControllerUpdate();

        // get sensor data
        SDL_GameControllerGetSensorData(gamepad, SDL_SENSOR_ACCEL, accel, num_data);
        SDL_GameControllerGetSensorData(gamepad, SDL_SENSOR_GYRO, gyro, num_data);
        SDL_GameControllerGetSensorData(gamepad, SDL_SENSOR_ACCEL_L, accel_l,
                                        num_data);
        SDL_GameControllerGetSensorData(gamepad, SDL_SENSOR_GYRO_L, gyro_l,
                                        num_data);
        SDL_GameControllerGetSensorData(gamepad, SDL_SENSOR_ACCEL_R, accel_r,
                                        num_data);
        SDL_GameControllerGetSensorData(gamepad, SDL_SENSOR_GYRO_R, gyro_r,
                                        num_data);

        // print sensor data
        SDL_Log("Accel [_]: %f, %f, %f", accel[0], accel[1], accel[2]);
        SDL_Log("Accel [L]: %f, %f, %f", accel_l[0], accel_l[1], accel_l[2]);
        SDL_Log("Accel [R]: %f, %f, %f", accel_r[0], accel_r[1], accel_r[2]);
        SDL_Log("Gyro  [_]: %f, %f, %f", gyro[0], gyro[1], gyro[2]);
        SDL_Log("Gyro  [L]: %f, %f, %f", gyro_l[0], gyro_l[1], gyro_l[2]);
        SDL_Log("Gyro  [R]: %f, %f, %f", gyro_r[0], gyro_r[1], gyro_r[2]);

        if (i < count - 1) {
            SDL_Log("\n");
            ;
            SDL_Delay(1000);
        }
    }
}

int main(int argc, char *argv[])
{
    // stop with <ctrl-c>
    std::signal(SIGINT, exit);

    print_sdl_version();

    print_hidapi_info();

    SDL_Init(SDL_INIT_GAMECONTROLLER);

    find_gamepad();
    enable_sensors();
    print_gamepad();
    print_sensors();
    return 0;
}

[slouken]

The issue here is that macOS and SDL are both trying to interact with the controllers. I fixed SDL getting the wrong calibration data in c94da89, but I keep having one or the other of the Joy-Con controllers being disconnected at the OS level. This happened even when I disabled the HIDAPI driver, so I'm not sure if the controllers are just flaky on macOS.

Can you try the latest main code and see if that works better for you?

[homma]

Thank you for your help.

I have tested for SDL-3.3.3-e24eeef.
And the result looks fine.

Accel [L]: 0.26197025, 10.173941, -0.8165723
Accel [R]: -0.23362799, 9.993438, -0.74016947

Thank you so much for the fix!

3.3.3-e24eeef-bluetooth.txt

[slouken]

You're welcome!