platypus

The Platypus sensor board

• Invensense MPU9250 IMU (3D accelerometer, 3D gyroscope, 
3D magnetometer, Temperature)
• Bosch BME280 (Humidity, Temperature, Barometric pressure)
• AMS TSL2584TSV Ambient Visible/IR Light Sensor
• Maxim MAX17043 Battery Gauge
• Sharp LS013B7DH03 128x128 Low-Power Display (Datasheet)
• or the Sharp LS013B4DN04 96x96 display

Board schematic

Note: In order to use the interrupt functionalities of the sensors, you may have to solder connections at the interrupt jumpers (J_IMU, J_BAT, J_ALS).

Note: Since we have changed the platypus board schematics multiple times throughout development, some boards may use a different I2C bus than others. If the sensors on your board don't work, try bus 6 instead of bus 1!

Testing the sensors

There is a script that automatically tests all attached sensors that might help you to debug particular problems:
setup according to edison/package-control, then

opkg update
opkg install wsnlab
platypus-test

Getting started with the display

There are already C drivers for the display (LcdDriver), that use a minimal graphics library (grlib). An example program which initializes the display and draws some stuff could look like this (dsptest.c):

Note: If you have the smaller 96px version of the display, use the Sharp96x96.h/.c driver.

#include "LcdDriver.h"
#include "Sharp128x128.h"
#include "grlib.h"

int main(int argc, const char* argv[]) {
    HAL_LCD_initDisplay(); // init display
    tContext g_sContext;
    Graphics_initContext(&g_sContext, &g_sharp128x128LCD); // init display context

    Graphics_setForegroundColor(&g_sContext, ClrWhite); // foreground color (text, drawings, etc.)
    Graphics_setBackgroundColor(&g_sContext, ClrBlack); // background color
    Graphics_setFont(&g_sContext, &g_sFontFixed6x8); // font (see grlib font folder)

    Graphics_clearDisplay(&g_sContext); // clear the display
    Graphics_flushBuffer(&g_sContext); // flush the changes (clear at this point)

    Graphics_drawLine(&g_sContext,118,11,126,11); // example for a line
    Graphics_drawCircle(&g_sContext, 50, 50, 20); // example for a circle
    Graphics_drawString(&g_sContext, "hello world", 12, 40, 40, OPAQUE_TEXT); // example for some text

    Graphics_flushBuffer(&g_sContext); // flush the changes (draws)
    printf("Done\n");

    return 0;
}

In a directory structure like this:

- [name]/
  - GrLib/
  - LcdDriver/
  - include/
  - lib/
  [name].cpp

compile the program with:

g++ -IGrLib/grlib -ILcdDriver -Iinclude -Llib -lmraa -lGrLib -lLcdDriver -lplatypus -o [name] [name].cpp 

Getting started with the IMU

Make yourself familiar with the IMU datasheet and especially the register map!

Note: Since we have changed the platypus board schematics multiple times throughout development, some boards may use a different I2C bus than others. If the sensors on your board don't work, try bus 6 instead of bus 1!

Some example C code that uses mraa to reset the IMU and read the current accelerometer values:

#include "mraa.h"

int main (int argc, const char* argv[]) {
    // init i2c comms
    mraa_i2c_context i2c = mraa_i2c_init(1); // i2c bus 1
    mraa_i2c_address(i2c, 0x68);
    uint8_t rx_tx_buf[2];

    // reset
    rx_tx_buf[0] = 0x6B; // power management 1
    rx_tx_buf[1] = 0x80; // set reset bit
    mraa_i2c_write(i2c, rx_tx_buf, 2);
    usleep(200000); // wait for reset

    // wakeup
    rx_tx_buf[0] = 0x6B; // power management 1
    rx_tx_buf[1] = 0x00; // unset sleep bit
    mraa_i2c_write(i2c, rx_tx_buf, 2);

    usleep(200000); // wait for new measurements

    // read raw accelerometer values
    uint8_t ax_rawH = mraa_i2c_read_byte_data(i2c, 0x3B);
    uint8_t ax_rawL = mraa_i2c_read_byte_data(i2c, 0x3C);
    uint8_t ay_rawH = mraa_i2c_read_byte_data(i2c, 0x3D);
    uint8_t ay_rawL = mraa_i2c_read_byte_data(i2c, 0x3E);
    uint8_t az_rawH = mraa_i2c_read_byte_data(i2c, 0x3F);
    uint8_t az_rawL = mraa_i2c_read_byte_data(i2c, 0x40);

    // convert high and low bytes to signed 16-bit integers
    int16_t ax_raw = (int16_t) ((ax_rawH<<8) + ax_rawL);
    int16_t ay_raw = (int16_t) ((ay_rawH<<8) + ay_rawL);
    int16_t az_raw = (int16_t) ((az_rawH<<8) + az_rawL);

    // convert to g
    float ax = ax_raw / 16384.0;
    float ay = ay_raw / 16384.0;
    float az = az_raw / 16384.0;

    printf("X: %f\n", ax);
    printf("Y: %f\n", ay);
    printf("Z: %f\n", az);

    return 0;
}

Compile with gcc -lmraa imutest.c -o imutest.

Code for the other sensors will work very similar to this, just look up the datasheets.