I've finally got something for post.
Last month I've been playing with the TI MSP430 Launchpad and when I work with ADC it lacks of visualization. Since Launchpad have UART-USB interface, I decided to plot incoming data.
I'm using MSP430G2553, and all code was written for this controller.
Firmware
Firmware of controller is pretty straightforward in large scale: it just sends value from ADC to the UART continously - with one note: before start to send anything, we need to make a "handshake" - receive start symbol from computer. So, high-level algorithm will be like this:
1) Initialize UART[1] (9600 baud) and ADC[2]
2) Wait for start signal ("handshake")
3) In forever loop send temperature to UART
ADC initialization to read temperature (10 channel):
void ADC_init(void) {
ADC10CTL0 = SREF_1 + REFON + ADC10ON + ADC10SHT_3;
ADC10CTL1 = INCH_10 + ADC10DIV_3;
}
int getTemperatureCelsius()
{
int t = 0;
__delay_cycles(1000); // Not neccessary.
ADC10CTL0 |= ENC + ADC10SC;
while (ADC10CTL1 & BUSY);
t = ADC10MEM;
ADC10CTL0 &=~ ENC;
return(int) ((t * 27069L - 18169625L) >> 16); // magic conversion to Celsius
}
Handshake:
// UART Handshake...
unsigned char c;
while ((c = uart_getc()) != '1');
uart_puts((char *)"\nOK\n");
We're waiting for '1' and sending "OK" when we receive it.
After that, program starts to send temperature indefinitely:
while(1) {
uart_printf("%i\n", getTemperatureCelsius());
P1OUT ^= 0x1;
}
uart_printf converts integer value into string and send over UART [3].
The source code of firmware in the bottom of this post.
Plotting Application
I love
matplotlib in python, it's great library to plot everything.To read data from UART, I used
pySerial library. That's all we need.
When we connect launchpad to computer, device /dev/ttyACM0 is created. It's serial port which we need to use.
Application consists of two threads:
- Serial port processing
- Continous plot updating
Serial port processing
Let's define global variable
data = deque(0 for _ in range(5000)), it will contain data to plot and
dataP = deque(0 for _ in range(5000)), it will contain approximated values.
In the serial port thread, we need to open connection:
ser = serial.Serial('/dev/ttyACM0', 9600, timeout=1)
then, make a "handshake":
ok = b''
while ok.strip() != b'OK':
ser.write(b"1")
ok = ser.readline()
print("Handshake OK!\n")
As you see, we're waiting the "OK" in response to "1". After "handshake", we can start reading data:
while True:
try:
val = int(ser.readline().strip())
addValue(val)
except ValueError:
pass
UART is not very stable, so sometimes you can receive distorted data. That's why I eat exceptions.
addValue here is function that processes data and puts it to
data variable:
avg = 0
def addValue(val):
global avg
data.append(val)
data.popleft()
avg = avg + 0.1 * (val - avg)
dataP.append(avg)
dataP.popleft()
Also it calculates weighted moving average:
Continous plot updating
First, let's create figure with two plots:
fig, (p1, p2) = plt.subplots(2, 1)
plot_data, = p1.plot(data, animated=True)
plot_processed, = p2.plot(data, animated=True)
p1.set_ylim(0, 100) # y limits
p2.set_ylim(0, 100)
To draw animated plot, we need to define function that will update data:
def animate(i):
plot_data.set_ydata(data)
plot_data.set_xdata(range(len(data)))
plot_processed.set_ydata(dataP)
plot_processed.set_xdata(range(len(dataP)))
return [plot_data, plot_processed]
ani = animation.FuncAnimation(fig, animate, range(10000),
interval=50, blit=True)
And show the plot window:
plt.show()
Here's the result of program's work:
On the first plot it's raw data received through serial port, on the second it's average.
Source codes
Desktop live plotting application:
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| import matplotlib.pyplot as plt
import matplotlib.animation as animation
import serial
import threading
from collections import deque
data = deque(0 for _ in range(5000))
dataP = deque(0 for _ in range(5000))
avg = 0
def addValue(val):
global avg
data.append(val)
data.popleft()
avg = avg + 0.1 * (val - avg)
dataP.append(avg)
dataP.popleft()
def msp430():
print("Connecting...")
ser = serial.Serial('/dev/ttyACM0', 9600, timeout=1)
print("Connected!")
# Handshake...
ok = b''
while ok.strip() != b'OK':
ser.write(b"1")
ok = ser.readline()
print(ok.strip())
print("Handshake OK!\n")
while True:
try:
val = int(ser.readline().strip())
addValue(val)
print(val)
except ValueError:
pass
if __name__ == "__main__":
threading.Thread(target=msp430).start()
fig, (p1, p2) = plt.subplots(2, 1)
plot_data, = p1.plot(data, animated=True)
plot_processed, = p2.plot(data, animated=True)
p1.set_ylim(0, 100)
p2.set_ylim(0, 100)
def animate(i):
plot_data.set_ydata(data)
plot_data.set_xdata(range(len(data)))
plot_processed.set_ydata(dataP)
plot_processed.set_xdata(range(len(dataP)))
return [plot_data, plot_processed]
ani = animation.FuncAnimation(fig, animate, range(10000),
interval=50, blit=True)
plt.show()
|
MSP430 full firmware:
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| /*
NOTICE
Used code or got an idea from:
UART: Stefan Wendler - http://gpio.kaltpost.de/?page_id=972
ADC: http://indiantinker.wordpress.com/2012/12/13/tutorial-using-the-internal-temperature-sensor-on-a-msp430/
printf: http://forum.43oh.com/topic/1289-tiny-printf-c-version/
*/
#include <msp430g2553.h>
// =========== HEADERS ===============
// UART
void uart_init(void);
void uart_set_rx_isr_ptr(void (*isr_ptr)(unsigned char c));
unsigned char uart_getc();
void uart_putc(unsigned char c);
void uart_puts(const char *str);
void uart_printf(char *, ...);
// ADC
void ADC_init(void);
// =========== /HEADERS ===============
// Trigger on received character
void uart_rx_isr(unsigned char c) {
P1OUT ^= 0x40;
}
int main(void)
{
WDTCTL = WDTPW + WDTHOLD;
BCSCTL1 = CALBC1_8MHZ; //Set DCO to 8Mhz
DCOCTL = CALDCO_8MHZ; //Set DCO to 8Mhz
P1DIR = 0xff;
P1OUT = 0x1;
ADC_init();
uart_init();
uart_set_rx_isr_ptr(uart_rx_isr);
__bis_SR_register(GIE); // global interrupt enable
// UART Handshake...
unsigned char c;
while ((c = uart_getc()) != '1');
uart_puts((char *)"\nOK\n");
ADC10CTL0 |= ADC10SC;
while(1) {
uart_printf("%i\n", getTemperatureCelsius());
P1OUT ^= 0x1;
}
}
// ========================================================
// ADC configured to read temperature
void ADC_init(void) {
ADC10CTL0 = SREF_1 + REFON + ADC10ON + ADC10SHT_3;
ADC10CTL1 = INCH_10 + ADC10DIV_3;
}
int getTemperatureCelsius()
{
int t = 0;
__delay_cycles(1000);
ADC10CTL0 |= ENC + ADC10SC;
while (ADC10CTL1 & BUSY);
t = ADC10MEM;
ADC10CTL0 &=~ ENC;
return(int) ((t * 27069L - 18169625L) >> 16);
}
// ========================================================
// UART
#include <legacymsp430.h>
#define RXD BIT1
#define TXD BIT2
/**
* Callback handler for receive
*/
void (*uart_rx_isr_ptr)(unsigned char c);
void uart_init(void)
{
uart_set_rx_isr_ptr(0L);
P1SEL = RXD + TXD;
P1SEL2 = RXD + TXD;
UCA0CTL1 |= UCSSEL_2; //SMCLK
//8,000,000Hz, 9600Baud, UCBRx=52, UCBRSx=0, UCBRFx=1
UCA0BR0 = 52; //8MHz, OSC16, 9600
UCA0BR1 = 0; //((8MHz/9600)/16) = 52.08333
UCA0MCTL = 0x10|UCOS16; //UCBRFx=1,UCBRSx=0, UCOS16=1
UCA0CTL1 &= ~UCSWRST; //USCI state machine
IE2 |= UCA0RXIE; // Enable USCI_A0 RX interrupt
}
void uart_set_rx_isr_ptr(void (*isr_ptr)(unsigned char c))
{
uart_rx_isr_ptr = isr_ptr;
}
unsigned char uart_getc()
{
while (!(IFG2&UCA0RXIFG)); // USCI_A0 RX buffer ready?
return UCA0RXBUF;
}
void uart_putc(unsigned char c)
{
while (!(IFG2&UCA0TXIFG)); // USCI_A0 TX buffer ready?
UCA0TXBUF = c; // TX
}
void uart_puts(const char *str)
{
while(*str) uart_putc(*str++);
}
interrupt(USCIAB0RX_VECTOR) USCI0RX_ISR(void)
{
if(uart_rx_isr_ptr != 0L) {
(uart_rx_isr_ptr)(UCA0RXBUF);
}
}
// ========================================================
// UART PRINTF
#include "stdarg.h"
static const unsigned long dv[] = {
// 4294967296 // 32 bit unsigned max
1000000000, // +0
100000000, // +1
10000000, // +2
1000000, // +3
100000, // +4
// 65535 // 16 bit unsigned max
10000, // +5
1000, // +6
100, // +7
10, // +8
1, // +9
};
static void xtoa(unsigned long x, const unsigned long *dp)
{
char c;
unsigned long d;
if(x) {
while(x < *dp) ++dp;
do {
d = *dp++;
c = '0';
while(x >= d) ++c, x -= d;
uart_putc(c);
} while(!(d & 1));
} else
uart_putc('0');
}
static void puth(unsigned n)
{
static const char hex[16] = { '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
uart_putc(hex[n & 15]);
}
void uart_printf(char *format, ...)
{
char c;
int i;
long n;
va_list a;
va_start(a, format);
while(c = *format++) {
if(c == '%') {
switch(c = *format++) {
case 's': // String
uart_puts(va_arg(a, char*));
break;
case 'c': // Char
uart_putc(va_arg(a, char));
break;
case 'i': // 16 bit Integer
case 'u': // 16 bit Unsigned
i = va_arg(a, int);
if(c == 'i' && i < 0) i = -i, uart_putc('-');
xtoa((unsigned)i, dv + 5);
break;
case 'l': // 32 bit Long
case 'n': // 32 bit uNsigned loNg
n = va_arg(a, long);
if(c == 'l' && n < 0) n = -n, uart_putc('-');
xtoa((unsigned long)n, dv);
break;
case 'x': // 16 bit heXadecimal
i = va_arg(a, int);
puth(i >> 12);
puth(i >> 8);
puth(i >> 4);
puth(i);
break;
case 0: return;
default: goto bad_fmt;
}
} else
bad_fmt: uart_putc(c);
}
va_end(a);
}
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Sources
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