Partial progress on period measurer.

project/Makefile

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+OBJECTS=main.o
+DEVICE  = msp430g2553
+INSTALL_DIR=$(HOME)/ti/msp430_gcc
+
+GCC_DIR =  $(INSTALL_DIR)/bin
+SUPPORT_FILE_DIRECTORY = $(INSTALL_DIR)/include
+
+CC      = $(GCC_DIR)/msp430-elf-gcc
+GDB     = $(GCC_DIR)/msp430-elf-gdb
+
+CFLAGS = -I $(SUPPORT_FILE_DIRECTORY) -mmcu=$(DEVICE) -O2 -g
+LFLAGS = -L $(SUPPORT_FILE_DIRECTORY) -T $(DEVICE).ld
+
+all: ${OBJECTS}
+	$(CC) $(CFLAGS) $(LFLAGS) $? -o main.elf
+
+main: main.c
+	$(CC) $(CFLAGS) $(LFLAGS) $? -S -o main.asm
+
+debug: all
+	$(GDB) main.elf

project/main.c

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+#include "msp430.h"
+
+#define   TXD       BIT2
+#define   RXD       BIT1
+
+#define   US        1000000
+
+unsigned int TXByte;
+
+void main(void) {
+  WDTCTL    = WDTPW + WDTHOLD;  // Stop WDT
+
+  BCSCTL1   = CALBC1_1MHZ;      // Set range
+  DCOCTL    = CALDCO_1MHZ;
+  BCSCTL2  &= ~(DIVS_3);        // SMCLK = DCO = 1 MHz
+
+  P1SEL     = BIT1 + BIT2;      // P1.1 = RXD, P1.2=TXD
+  P1SEL2    = BIT1 + BIT2;      // P1.1 = RXD, P1.2=TXD
+  UCA0CTL1 |= UCSSEL_2;         // Use SMCLK
+  UCA0BR0   = 104;              // Set baud rate to 9600 with 1MHz clock (Data Sheet 15.3.13)
+  UCA0BR1   = 0;                // Set baud rate to 9600 with 1MHz clock
+  UCA0MCTL  = UCBRS0;           // Modulation UCBRSx = 1
+  UCA0CTL1 &= ~UCSWRST;         // Initialize USCI state machine
+
+  P1DIR    |= TXD;
+  P1OUT    |= TXD;
+
+  P1DIR |= BIT0;
+
+  TACTL     = TACLR;            // reset clock
+  TACTL     = TASSEL_2 | MC_2;  // set SMCLK timer to count up at 1 MHz
+  TACCTL0   = CM1 | SCS | CAP | CCIE;   // set capture mode to rising edge and enable interrupts
+  
+  while (1) {
+    TAR = 0;
+    P1OUT ^= BIT0;
+    __enable_interrupt();
+    __bis_SR_register(LPM0_bits + GIE);
+    TXByte = US/TACCR0;                 // frequency in Hz
+    
+    TXByte /= 2;                        // frequency won't fit in a byte
+    while (!(IFG2 & UCA0TXIFG));        // wait for TX buffer to be ready for new data
+    UCA0TXBUF = TXByte;           
+
+    __delay_cycles(100000);             // wait >10 ms before measuring again
+  }
+}
+
+#if defined(__TI_COMPILER_VERSION__)
+#pragma vector=TIMER0_A0_VECTOR
+__interrupt void timer0_a0_isr(void)
+#else
+  void __attribute__ ((interrupt(TIMER0_A0_VECTOR))) timer0_a0_isr (void)
+#endif
+{
+  TACCTL0 &= ~CCIFG;                    // set interrupt flag to 0
+  __disable_interrupt();                // disable interrupts
+  __bic_SR_register_on_exit(LPM0_bits); // take us out of low power mode
+} 

project/measurements.csv

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+Distance (cm), Measured (cm),,Difference (cm)
+1,3,2,1
+1.5,3,2,0.5
+2,3,2,0
+2.5,3,2,-0.5
+3,4,3,0
+3.5,4,3,-0.5
+4,5,4,0
+4.5,5,4,-0.5
+5,6,5,0
+6,7,6,0
+7,8,7,0
+8,9,8,0
+9,10,9,0
+10,11,10,0
+15,16,15,0
+20,21,20,0
+25,26,25,0
+30,31,30,0
+40,41,40,0
+50,51,50,0
+60,61,60,0
+80,81,80,0
+100,101,100,0
+120,122,121,1
+140,142,141,1
+160,162,161,1
+180,183,182,2
+200,203,202,2

project/python-serial-plot.py

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+#!/usr/bin/python2.7
+import serial # for serial port
+import numpy as np # for arrays, numerical processing
+from time import sleep,time
+import gtk #the gui toolkit we'll use:
+# graph plotting library:
+from matplotlib.figure import Figure
+from matplotlib.backends.backend_gtkagg import FigureCanvasGTKAgg as FigureCanvas
+
+#needs: python2, pyserial, numpy, matplotlib, pygtk
+#0) flash the serial temperature measurement program into the msp430
+#1) start this program
+#2) press the button the Launchpad to enter 'applcation mode'
+#3) warm the chip (eg with a light bulb or your fingers)
+#4) when you've seen enough, press the reset button on the launchpad
+#5) exit the program by pressing 'q' or clicking on the x
+
+#define the serial port. Pick one:
+port = "/dev/ttyACM0"  #for Linux
+#port = "COM5" #For Windows?
+#port = "/dev/tty.uart-XXXX" #For Mac?
+
+#function that gets called when a key is pressed:
+def press(event):
+    print('press', event.key)
+    if event.key == 'q':
+        print ('got q!')
+        quit_app(None)
+    return True
+    
+def quit_app(event):
+    outFile.close()
+    ser.close()
+    quit()
+
+#start our program proper:
+#open the serial port
+try:
+    ser = serial.Serial(port,2400,timeout = 0.050)
+    ser.baudrate=9600
+# with timeout=0, read returns immediately, even if no data
+except:
+    print ("Opening serial port",port,"failed")
+    print ("Edit program to point to the correct port.")
+    print ("Hit enter to exit")
+    raw_input()
+    quit()
+
+#create a window to put the plot in
+win = gtk.Window()
+#connect the destroy signal (clicking the x in the corner)
+win.connect("destroy", quit_app)
+win.set_default_size(400,300)
+
+yvals = np.zeros(50) #array to hold last 50 measurements
+times=np.arange(0,50,1.0) # 50 from 0 to 49.
+
+#create a plot:
+fig = Figure()
+ax = fig.add_subplot(111,xlabel='Time Step',ylabel='Distance (cm)')
+ax.set_ylim(0,255) # set limits of y axis.
+
+canvas = FigureCanvas(fig) #put the plot onto a canvas
+win.add(canvas) #put the canvas in the window
+
+# define a callback for when a key is pressed
+fig.canvas.mpl_connect('key_press_event',press)
+
+#show the window
+win.show_all()
+win.set_title("ready to receive data");
+
+line, = ax.plot(times,yvals)
+#open a data file for the output
+outFile = open("time_and_dist.txt","w")
+start_time = time()
+ser.flushInput()
+
+while(1): #loop forever
+    data = ser.read(1) # look for a character from serial port, will wait up to timeout above.
+    if len(data) > 0: #was there a byte to read? should always be true.
+        yvals = np.roll(yvals,-1) # shift the values in the array
+        yvals[49] = ord(data) # take the value of the byte
+        outFile.write(str(time()-start_time)+" "+str(yvals[49])+"\n") #write to file
+        line.set_ydata(yvals) # draw the line
+        fig.canvas.draw() # update the canvas
+        win.set_title("Distance: "+str(yvals[49])+" cm")
+    while gtk.events_pending():	#makes sure the GUI updates
+        gtk.main_iteration()
+#    sleep(.05) # don't eat the cpu. This delay limits the data rate to ~ 200 samples/s

project/python-serial-print.py

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+#!/usr/bin/python2.7
+import serial # for serial port
+import numpy as np # for arrays, numerical processing
+
+#needs: python2, pyserial, numpy, 
+#0) flash the serial temperature measurement program into the msp430
+#1) start this program
+#2) press the button the Launchpad to enter 'applcation mode'
+#3) warm the chip (eg with a light bulb or your fingers)
+#4) when you've seen enough, press the reset button on the launchpad
+#5) exit the program by pressing 'q' or clicking on the x
+
+#define the serial port. Pick one:
+port = "/dev/ttyACM0"  #for Linux
+#port = "COM5" #For Windows?
+#port = "/dev/tty.uart-XXXX" #For Mac?
+
+
+#start our program proper:
+#open the serial port
+try:
+    ser = serial.Serial(port,2400,timeout = 0.050) 
+    ser.baudrate=9600
+# with timeout=0, read returns immediately, even if no data
+except:
+    print ("Opening serial port",port,"failed")
+    print ("Edit program to point to the correct port.")
+    print ("Hit enter to exit")
+    raw_input()
+    quit()
+
+ser.flushInput()
+
+while(1): #loop forever
+    data = ser.read(1) # look for a character from serial port - will wait for up to 50ms (specified above in timeout)
+    if len(data) > 0: #was there a byte to read?
+        print ord(data)

project/serial_duplex.c

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+/* Example code demonstrating the use of the hardware UART on the MSP430G2553 to receive
+ * and transmit data back to a host computer over the USB connection on the MSP430
+ * launchpad.
+ * Note: After programming it is necessary to stop debugging and reset the uC before
+ * connecting the terminal program to transmit and receive characters.
+ * This demo will turn on the Red LED if an R is sent and turn it off if a r is sent.
+ * Similarly G and g will turn on and off the green LED
+ * It also transmits the received character back to the terminal.
+
+FROM: https://bennthomsen.wordpress.com/engineering-toolbox/ti-msp430-launchpad/msp430g2553-hardware-uart/
+
+
+ */
+  
+#include "msp430.h"
+void UARTSendArray(char *TxArray, char ArrayLength);
+  
+static  char data;
+  
+void main(void)
+  
+{
+ WDTCTL = WDTPW + WDTHOLD; // Stop WDT
+  
+ P1DIR |= BIT0 + BIT6; // Set the LEDs on P1.0, P1.6 as outputs
+ P1OUT = BIT0; // Set P1.0
+  
+ BCSCTL1 = CALBC1_1MHZ; // Set DCO to 1MHz
+ DCOCTL = CALDCO_1MHZ; // Set DCO to 1MHz
+  
+/* Configure hardware UART */
+ P1SEL = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
+ P1SEL2 = BIT1 + BIT2 ; // P1.1 = RXD, P1.2=TXD
+ UCA0CTL1 |= UCSSEL_2; // Use SMCLK
+ UCA0BR0 = 104; // Set baud rate to 9600 with 1MHz clock (Data Sheet 15.3.13)
+ UCA0BR1 = 0; // Set baud rate to 9600 with 1MHz clock
+ UCA0MCTL = UCBRS0; // Modulation UCBRSx = 1
+ UCA0CTL1 &= ~UCSWRST; // Initialize USCI state machine
+ IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt
+  
+__bis_SR_register(LPM0_bits + GIE); // Enter LPM0, interrupts enabled
+}
+  
+// Echo back RXed character, confirm TX buffer is ready first
+
+#if defined(__TI_COMPILER_VERSION__)
+#pragma vector=USCIAB0RX_VECTOR
+__interrupt void USCI0RX_ISR(void)
+#else
+  void __attribute__ ((interrupt(USCIAB0RX_VECTOR))) uci0rx_isr(void)
+#endif
+{
+data = UCA0RXBUF;
+UARTSendArray("Received command: ", 18); 
+UARTSendArray(&data, 1);
+UARTSendArray("\n\r", 2);
+  
+switch(data){
+ case 'R':
+ {
+ P1OUT |= BIT0;
+ }
+ break;
+ case 'r':
+ {
+ P1OUT &= ~BIT0;
+ }
+ break;
+ case 'G':
+ {
+ P1OUT |= BIT6;
+ }
+ break;
+ case 'g':
+ {
+ P1OUT &= ~BIT6;
+ }
+ break;
+ default:
+ {
+ UARTSendArray("Unknown Command: ", 17);
+ UARTSendArray(&data, 1);
+ UARTSendArray("\n\r", 2);
+ }
+ break;
+ }
+}
+  
+void UARTSendArray(char *TxArray,  char ArrayLength){
+ // Send number of bytes Specified in ArrayLength in the array at using the hardware UART 0
+ // Example usage: UARTSendArray("Hello", 5);
+ // int data[2]={1023, 235};
+ // UARTSendArray(data, 4); // Note because the UART transmits bytes it is necessary to send two bytes for each integer hence the data length is twice the array length
+  
+while(ArrayLength--){ // Loop until StringLength == 0 and post decrement
+ while(!(IFG2 & UCA0TXIFG)); // Wait for TX buffer to be ready for new data
+ UCA0TXBUF = *TxArray; //Write the character at the location specified py the pointer
+ TxArray++; //Increment the TxString pointer to point to the next character
+ }
+}