MSP 430 Semester Project ECE 300 Circuits MSP

MSP 430 Semester Project ECE 300 Circuits

MSP 430 16 Bit RISC Micro-controller Low Power 12 Bit A/D Converter 6 Digital I/O ports (8 lines per port) 2 UARTs for Serial Communication

Load Cell Weight Pad Aluminum Load cell with embedded strain gauge The strain gauge requires an “excitation voltage” The output voltage needs to be amplified

Max 4238 Ultra-Low Offset/Drift, Low-Noise, Precision SOT 23 Amplifiers Can Operate from a single 2. 7 V – 5. 5 V Supply Rail to Rail Outputs Near-zero DC offset and drift

Typical Circuit

12 Bit - ADC Op-amp amplifying by a factor of ~ 115 Strain gauge outputs 1. 992 m. V /V of excitation at full load 115 x 3. 3 X. 001992 V = 0. 756 V at full load Use Analogue Reference of 1. 5 V Only using about half the resolution of the ADC Can only resolve down to about 0. 012 Kg

Plot of Calibration Data

Increase the Update Rate // set up Basic Timer IE 2 |= BTIE; // Enable BT interrupt //BTCTL = BT_ADLY_2000 | BT_f. LCD_DIV 256; // Original Code BTCTL = BT_ADLY_32 | BT_f. LCD_DIV 256; // 32 ms Interrupt // set up ADC 12 IE |= 0 x 0040; // Enable ADC 6 interrupt //ADC 12 CTL 0 = ADC 12 ON + REF 2_5 V + REFON; // Original ADC 12 CTL 0 = ADC 12 ON + REFON; // Aref = 1. 5 V, Aref on ADC 12 CTL 1 = CSTARTADD_6 + ADC 12 SSEL_1 + SHP; ADC 12 MCTL 6 = SREF_1 + INCH_6; ADC 12 CTL 0 |= ENC ; //Enables ADC

Defined in MSP 430. h /* with assumed vlues of f. ACLK=32 KHz, f. MCLK=1 MHz */ /* f. BT=f. ACLK is thought for longer interval times */ #define BT_ADLY_0_064 (0 x 00) /* 0. 064 ms interval (default) */ #define BT_ADLY_0_125 (BTIP 0) /* 0. 125 ms " */ #define BT_ADLY_0_25 (BTIP 1) /* 0. 25 ms " */ #define BT_ADLY_0_5 (BTIP 1+BTIP 0) /* 0. 5 ms " */ #define BT_ADLY_1 (BTIP 2) /* 1 ms " */ #define BT_ADLY_2 (BTIP 2+BTIP 0) /* 2 ms " */ #define BT_ADLY_4 (BTIP 2+BTIP 1) /* 4 ms " */ #define BT_ADLY_8 (BTIP 2+BTIP 1+BTIP 0) /* 8 ms " */ #define BT_ADLY_16 (BTDIV) /* 16 ms " */ #define BT_ADLY_32 (BTDIV+BTIP 0) /* 32 ms " */ #define BT_ADLY_64 (BTDIV+BTIP 1) /* 64 ms " */ #define BT_ADLY_125 (BTDIV+BTIP 1+BTIP 0) /* 125 ms " */ #define BT_ADLY_250 (BTDIV+BTIP 2) /* 250 ms " */ #define BT_ADLY_500 (BTDIV+BTIP 2+BTIP 0) /* 500 ms " */ #define BT_ADLY_1000 (BTDIV+BTIP 2+BTIP 1) /* 1000 ms " */ #define BT_ADLY_2000 (BTDIV+BTIP 2+BTIP 1+BTIP 0) /* 2000 ms " */

Features to Add Increase excitation voltage Tare Button Conversion from Kg to Lbs Calibration Mode Use SPI to link Multiple Weight pads to one MSP 430

Questions