Capacitive Joystick Prototype

While I contributed to Active Games at Frankfurt University this year I digged a bit deeper into the capabilities of Cypress PSoC 4. I already played a bit with the capsense feature to realize touch-buttons or sliders. This time I went for the proximity sensor.

I started by connecting a single wire to the PSoC4 and enable the proximity sensor feature for it while sending the raw data via UART. I was impressed by the sensibility and also the S/N ratio. I attached a longer wire to the pin and was able to detect my body even if I was ~1m away. Of course my capacity sensor was not optimized but with that result from just “trial and error” I am pretty sure that you can make it a lot more sensitive if you spend some time reading about how to design the sensor (and not just use a wire).

However, the idea of Active Games is to develop and implement bodily user interfaces so i decided to give it a try and make my own capacitive joystick using proximity sensors.

The actual implementation is relative easy. I use 2 proximity sensors and subtract the values to get the X-Axis while I sum them up to get the Y-Axis. I send this data to a Freescale FRDM-KL25Z with a modified USB-HID library to make a USB-Joystick out of it.

I modified the mbed USBDevice library and ended up with a keyboard, joystick and media control, all in one.

static uint8_t reportDescriptor[] = {
                // Keyboard
                USAGE_PAGE(1),          0x01,
                USAGE(1),               0x06,
                COLLECTION(1),          0x01,
                REPORT_ID(1),           REPORT_ID_KEYBOARD,
                USAGE_PAGE(1),          0x07,
                USAGE_MINIMUM(1),       0xE0,
                USAGE_MAXIMUM(1),       0xE7,
                LOGICAL_MINIMUM(1),     0x00,
                LOGICAL_MAXIMUM(1),     0x01,
                REPORT_SIZE(1),         0x01,
                REPORT_COUNT(1),        0x08,
                INPUT(1),               0x02,
                REPORT_COUNT(1),        0x01,
                REPORT_SIZE(1),         0x08,
                INPUT(1),               0x01,
                REPORT_COUNT(1),        0x05,
                REPORT_SIZE(1),         0x01,
                USAGE_PAGE(1),          0x08,
                USAGE_MINIMUM(1),       0x01,
                USAGE_MAXIMUM(1),       0x05,
                OUTPUT(1),              0x02,
                REPORT_COUNT(1),        0x01,
                REPORT_SIZE(1),         0x03,
                OUTPUT(1),              0x01,
                REPORT_COUNT(1),        0x06,
                REPORT_SIZE(1),         0x08,
                LOGICAL_MINIMUM(1),     0x00,
                LOGICAL_MAXIMUM(2),     0xff, 0x00,
                USAGE_PAGE(1),          0x07,
                USAGE_MINIMUM(1),       0x00,
                USAGE_MAXIMUM(2),       0xff, 0x00,
                INPUT(1),               0x00,
                END_COLLECTION(0),

                // Joystick
                USAGE_PAGE(1),          0x01,           // Generic Desktop
                USAGE(1),               0x04,           // Joystick
                COLLECTION(1),          0x01,           // Application
                USAGE(1),               0x01,           // Pointer
                COLLECTION(1),          0x00,           // Physical
                REPORT_ID(1),           REPORT_ID_MOUSE,
                
                REPORT_COUNT(1),        0x03,
                REPORT_SIZE(1),         0x01,
                USAGE_PAGE(1),          0x09,           // Buttons
                USAGE_MINIMUM(1),       0x1,
                USAGE_MAXIMUM(1),       0x3,
                LOGICAL_MINIMUM(1),     0x00,
                LOGICAL_MAXIMUM(1),     0x01,
                INPUT(1),               0x02,    
                            
                REPORT_COUNT(1),        0x01,
                REPORT_SIZE(1),         0x05,
                INPUT(1),               0x01,
                
                REPORT_COUNT(1),        0x02,
                REPORT_SIZE(1),         0x08,
                USAGE_PAGE(1),          0x01,
                USAGE(1),               0x30,           // X
                USAGE(1),               0x31,           // Y
              //  USAGE(1),             0x32,           // Z
                LOGICAL_MINIMUM(1),     0x81,
                LOGICAL_MAXIMUM(1),     0x7f,
                INPUT(1),               0x02,
                
                END_COLLECTION(0),
                END_COLLECTION(0),


                // Media Control
                USAGE_PAGE(1),         0x0C,
                USAGE(1),              0x01,
                COLLECTION(1),         0x01,
                REPORT_ID(1),          REPORT_ID_VOLUME,
                USAGE_PAGE(1),         0x0C,
                LOGICAL_MINIMUM(1),    0x00,
                LOGICAL_MAXIMUM(1),    0x01,
                REPORT_SIZE(1),        0x01,
                REPORT_COUNT(1),       0x07,
                USAGE(1),              0xB5,             // Next Track
                USAGE(1),              0xB6,             // Previous Track
                USAGE(1),              0xB7,             // Stop
                USAGE(1),              0xCD,             // Play / Pause
                USAGE(1),              0xE2,             // Mute
                USAGE(1),              0xE9,             // Volume Up
                USAGE(1),              0xEA,             // Volume Down
                INPUT(1),              0x02,             // Input (Data, Variable, Absolute)
                REPORT_COUNT(1),       0x01,
                INPUT(1),              0x01,
                END_COLLECTION(0),
        };