GENERAL OBJETIVE:
Input Devices
Measure something: add a sensor to a microcontroller board that you have designed and read it
For the assignment of this week will be held hello.RGB.45 card as proof of an output device. For this file (PNG)
Once downloaded using FabModules the PCB was machined on a copper plate
Once you finished machining the following result is achieved:
After some sanding to remove burrs from the plate and facilitate the welding process is obtained:
Once the plate is free from burrs, it is easier to solder the components and once all have been welded components results in:
Once you have the plate welded components and connectors list programming can be done, for this we will use the following code in C language
//
//
// hello.temp.45.c
//
// thermistor hello-world
// 9600 baud FTDI interface
//
// Neil Gershenfeld
// 10/27/10
//
// (c) Massachusetts Institute of Technology 2010
// This work may be reproduced, modified, distributed,
// performed, and displayed for any purpose. Copyright is
// retained and must be preserved. The work is provided
// as is; no warranty is provided, and users accept all
// liability.
//
#include <avr/io.h>
#include <util/delay.h>
#define output(directions,pin) (directions |= pin) // set port direction for output
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
#define bit_delay_time 102 // bit delay for 9600 with overhead
#define bit_delay() _delay_us(bit_delay_time) // RS232 bit delay
#define half_bit_delay() _delay_us(bit_delay_time/2) // RS232 half bit delay
#define char_delay() _delay_ms(10) // char delay
#define serial_port PORTB
#define serial_direction DDRB
#define serial_pin_out (1 << PB2)
void put_char(volatile unsigned char *port, unsigned char pin, char txchar) {
//
// send character in txchar on port pin
// assumes line driver (inverts bits)
//
// start bit
//
clear(*port,pin);
bit_delay();
//
// unrolled loop to write data bits
//
if bit_test(txchar,0)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,1)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,2)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,3)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,4)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,5)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,6)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
if bit_test(txchar,7)
set(*port,pin);
else
clear(*port,pin);
bit_delay();
//
// stop bit
//
set(*port,pin);
bit_delay();
//
// char delay
//
bit_delay();
}
int main(void) {
//
// main
//
static char chr;
//
// set clock divider to /1
//
CLKPR = (1 << CLKPCE);
CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
//
// initialize output pins
//
set(serial_port, serial_pin_out);
output(serial_direction, serial_pin_out);
//
// init A/D
//
ADMUX = (0 << REFS2) | (0 << REFS1) | (0 << REFS0) // VCC ref
| (0 << ADLAR) // right adjust
| (0 << MUX3) | (1 << MUX2) | (1 << MUX1) | (1 << MUX0); // 20(PB4-PB3)
ADCSRA = (1 << ADEN) // enable
| (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0); // prescaler /128
ADCSRB = (1 << BIN); // bipolar mode
//
// main loop
//
while (1) {
//
// send framing
//
put_char(&serial_port, serial_pin_out, 1);
char_delay();
put_char(&serial_port, serial_pin_out, 2);
char_delay();
put_char(&serial_port, serial_pin_out, 3);
char_delay();
put_char(&serial_port, serial_pin_out, 4);
char_delay();
//
// initiate conversion
//
ADCSRA |= (1 << ADSC);
//
// wait for completion
//
while (ADCSRA & (1 << ADSC))
;
//
// send result
//
chr = ADCL;
put_char(&serial_port, serial_pin_out, chr);
char_delay();
chr = ADCH;
put_char(&serial_port, serial_pin_out, chr);
char_delay();
}
}
And Python code:
#
# hello.temp.45.py
#
# receive and display temperature
# hello.temp.45.py serial_port
#
# Neil Gershenfeld
# CBA MIT 3/27/12
#
# (c) Massachusetts Institute of Technology 2012
# Permission granted for experimental and personal use;
# license for commercial sale available from MIT
#
from Tkinter import *
from numpy import log
import serial
WINDOW = 600 # window size
eps = 0.5 # filter time constant
filter = 0.0 # filtered value
def idle(parent,canvas):
global filter, eps
#
# idle routine
#
byte2 = 0
byte3 = 0
byte4 = 0
ser.flush()
while 1:
#
# find framing
#
byte1 = byte2
byte2 = byte3
byte3 = byte4
byte4 = ord(ser.read())
if ((byte1 == 1) & (byte2 == 2) & (byte3 == 3) & (byte4 == 4)):
break
low = ord(ser.read())
high = ord(ser.read())
value = 256*high + low
if (value > 511):
value -= 1024
V = 2.5 - value*5.0/(20.0*512.0)
R = 10000.0/(5.0/V-1.0)
# NHQ103B375R5
# R25 10000 (O)
# B (25/85) 3750 (K)
# R(T(C)) = R(25)*exp(B*(1/(T(C)+273.15)-(1/(25+273.15))))
B = 3750.0
R25 = 10000.0
T = 1.0/(log(R/R25)/B+(1/(25.0+273.15))) - 273.15
filter = (1-eps)*filter + eps*T
x = int(.2*WINDOW + (.9-.2)*WINDOW*(filter-20.0)/10.0)
canvas.itemconfigure("text",text="%.2f"%filter)
canvas.coords('rect1',.2*WINDOW,.05*WINDOW,x,.2*WINDOW)
canvas.coords('rect2',x,.05*WINDOW,.9*WINDOW,.2*WINDOW)
canvas.update()
parent.after_idle(idle,parent,canvas)
#
# check command line arguments
#
if (len(sys.argv) != 2):
print "command line: hello.temp.45.py serial_port"
sys.exit()
port = sys.argv[1]
#
# open serial port
#
ser = serial.Serial(port,9600)
ser.setDTR()
#
# start plotting
#
root = Tk()
root.title('hello.temp.45.py (q to exit)')
root.bind('q','exit')
canvas = Canvas(root, width=WINDOW, height=.25*WINDOW, background='white')
canvas.create_text(.1*WINDOW,.125*WINDOW,text=".33",font=("Helvetica", 24),tags="text",fill="#0000b0")
canvas.create_rectangle(.2*WINDOW,.05*WINDOW,.3*WINDOW,.2*WINDOW, tags='rect1', fill='#b00000')
canvas.create_rectangle(.3*WINDOW,.05*WINDOW,.9*WINDOW,.2*WINDOW, tags='rect2', fill='#0000b0')
canvas.pack()
root.after(100,idle,root,canvas)
root.mainloop()
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