The Color Sensor Abstract. Project TI2849

Transcription

1 The Color Sensor Abstract Project TI849

2 Color Color is a notoriously subjective experience. While people can be very particular about the colors they use for lighting, designs, or environments, human perception of color is very subjective. The problem is even more significant as more environments turn to LED lighting for energy savings. LEDs often produce white by mixing red, green and blue primary colors. It s difficult for people to accurately judge the color balance objectively without resorting to measuring tools. Color Sensor Design The Color Sensor is a simple to use, low cost tool for getting accurate color readings from both reflected and emitted light. It gives accurate readings in multiple intuitive formats, both on a built-in LCD display, and also on a web page available over a local network. The Color Sensor is lightweight and portable, making it easy to use in a variety of environments. The Color Sensor uses the TI/Stellaris LM3S9B96 MCU to control all operations. The MCU communicates with the color sensor over using the built-in IC interface, the LCD display using a modified SPI protocol, the Ethernet using the built-in Ethernet controller, serial IO for system debugging and number of switches and indicators via parallel I/O. Color LCD Display Switches X > 4 Avago Color Sensor LED EKK-LM3S9B96 EVK Power +3.3V, Ethernet Serial To Local Network Figure - Block Diagram To PC

3 All of these communication channels are available simultaneously thanks to the built-in SafeRTOS operating system. The OS handles communication channels with independent concurrent tasks, so they re all live at the same time. There s no need to switch communication modes. Construction The prototype for the Color Sensor was constructed from numerous modules available as breakout boards, including the sensor itself, the LCD display, and the EKK-LM3S9B96 Evaluation Kit. These are mounted on a custom-made PCB that also provides battery power using two AA cells and a step-up boost converter to provide the 5V required by the EKK-LM3S9B96. Use The Color Sensor is simple to use. Below the display, two controls are provided, >, for move to the next screen, and X, for take action on this screen. The first screen is for calibration. The Avago ADJD-S37-v sensor used has a wide dynamic range. By pointing a white light (or white object) at the sensor and hitting the X button, the sensor adjusts the gain and the sense interval to maximize the dynamic range of the actual color readings. Pressing > takes you to the next screen, which allows you to toggle the sensor s built-in illumination LED for reading reflected light. Pressing > takes you to a screen with direct RGB readouts. This is useful if you re trying to, for example, calibrate two different light sources to produce the same output. Finally, the last > takes you to a hue / saturation color chart. The sensor s reading is plotted on the chart, providing an intuitive representation of the color (numerical results are also provided at the bottom). In both the RGB and HS screens, pressing X toggles the sensor updates. A final press of > takes you back to the calibration screen. Accessing the color sensor over the network displays a page with the RGB and hue / saturation plots of the sensor s current reading. Controls are also provided on the web page for calibration and toggling the sensor s LED.

4 Schematic IC6 PC4 PC5 PC6 PC7 SHDN LM3S9B96_TL IC7 PJ0 PJ PJ PJ3 PJ4 PJ5 PJ6 PJ7 PG0 PG7 VBUS PH0 PH PH PH5 PH6 PH7 PG LM3S9B96_TR PD0 PD PD PD3 PD4 PD5 PD6 PD7 SW ToggleSwitch 50F C L uh U 3/5\ LX SHDN\ OUT LBI LBO REF MAX756 D N587 0,F C3 00F C8 0,F C IC4 Vin L493CZ33 Vout,µF + C4 +3.3V +3.3V FTDI RTS RXD TXD CTS RED GRN BLU J IC /SW /SW 3 PE0 PF0 /CS PE PF JUMPER3 SCK PE PF/ENLED J3 J4 J5 IC PA0/RX PA/TX PA PA3 PA4 PA5 PA6 PA7 LM3S9B96_BL_Pads PE3 PE4 PE5 PE6 PE7 LM3S9B96_BR R PB/IC0SCL PB3/IC0SDA PB4/BTN PB5 PB6 PB7 PF3/ENLED PF4 PF5 3.3V IC5 DIO /RESET LED_GRN LED_BLU LED_RED 3.3V VBATT NokiaLCD IC3 3.3v SCL SDA LED SensorBreakout +3.3V N3906 T R 5K R,5K J ToggleSwitch SW Code Sample This sample shows the initialization and main loop of the task for managing the color sensor. static void SensorTask( void *pvparameters ) const portticktype delaytime = 000; unsigned short readings[4]; float h, s, L; // // Loop forever // while ()

5 // Interval to wait between samples xtaskdelay( delaytime ); switch (g_sensormode) case krgbupdate: measure(); read_reg_set( DATA_BASE, readings ); lcd_draw_rgb( readings[0], readings[], readings[] ); break; case khslupdate: sens_read_hsl( &h, &s, &L ); lcd_draw_hsl( h, s, L ); break; case knoupdate: default: break; unsigned long SensorTaskInit(void) unsigned char tmp; // Initialize the IC channel the sensor is connected to ROM_SysCtlPeripheralEnable( SYSCTL_PERIPH_GPIOB ); ROM_SysCtlPeripheralEnable( SYSCTL_PERIPH_IC0 ); GPIOPinConfigure( GPIO_PB_IC0SCL ); GPIOPinConfigure( GPIO_PB3_IC0SDA ); GPIOPinTypeIC( GPIO_PORTB_BASE, GPIO_PIN_ GPIO_PIN_3 ); // GPIO A Periph already enabled for the UART // Sensor illumination LED ROM_GPIOPinTypeGPIOOutput(GPIO_PORTA_BASE, GPIO_PIN_); // Set the clock (false = "slow" = 00kbps) ROM_ICMasterInitExpClk( IC0_MASTER_BASE, SysCtlClockGet(), false ); ROM_ICMasterEnable( IC0_MASTER_BASE ); tmp = read_register8( CAP_RED ); UARTprintf( "Cap red= %d\n", (int) tmp ); sens_set_integrate_time( 048 ); // Mid-range sens_calibrate( false ); // Create the task g_sensormode = knoupdate; if(xtaskcreate(sensortask, (signed portchar *)"Sensor", (signed portchar *)g_pulsensortaskstack, sizeof(g_pulsensortaskstack), NULL, PRIORITY_SENSOR_TASK,

6 return(); // Success return 0; NULL)!= pdpass)