- 1). Open a code editing application or use a text editing application such as TextEdit in Mac OS X or Notepad in Microsoft Windows. Create a new document to house the script of the Python oscilloscope.
- 2). Define the parameters that will be used in the script, as well as the two Python libraries needed for the script by using the following code:
import os, sys
import Image
import serial
import pygame
import time
from pyBusPirateLite.UART import *
from pyBusPirateLite.BitBang import * - 3). Define the data rate and use the print function to enable the program to graph the inputs made by the oscilloscope:
DATA_RATE = 5720.0 #measures/second (estimated experimenticaly)
DEFAULT_TIME_SCALE = RES_X / DATA_RATE #default time in seconds to make one window fill
pygame.init()
bp = UART(BUS_PIRATE_DEV,115200)
print "Entering binmode: ",
if bp.BBmode():
print "OK."
else:
print "failed."
sys.exit() - 4). Define the parameters for the application window by using the pygame.display function:
window = pygame.display.set_mode((RES_X, RES_Y))
background = (0,0,0)
line = (0,255,0)
trig_color = (100,100,0) - 5). Create the script for the oscilloscope itself by defining the parameters that will be written on the graph and providing arguments for the x and y-axis:
bp.port.write("\x15")
while 1:
plot = {}
voltage = {}
maxv = 0
minv = 100
time_scale = DEFAULT_TIME_SCALE * time_div
prev_voltage = 0
measure = 0;
if(trig_mode != NO_SYNC):
for k in range(1,2000):
prev_voltage = voltage
measure = bp.response(2, True)
voltage = ord(measure[0]) << 8
voltage = voltage + ord(measure[1])
voltage = (voltage/1024.0) * 6.6
#rising slope
if((voltage >= trigger_level) and (prev_voltage < (voltage * TRIG_CAL)) and (trig_mode == RISING_SLOPE)):
break
if((voltage < trigger_level) and (voltage > 0.01) and (prev_voltage > voltage/TRIG_CAL) and (trig_mode == FALLING_SLOPE)):
break
for i in range(RES_X):
for k in range(time_div - 1):
#ignoring (time_div-1) samples to achieve proper time resolution
bp.response(2, True)
measure = bp.response(2, True)
voltage = ord(measure[0]) << 8
voltage = voltage + ord(measure[1])
voltage = (voltage/1024.0) * 6.6
plot[i] = voltage
for i in range(1,RES_X):
if plot[i] > maxv:
maxv = plot[i]
if plot[i] < minv:
minv = plot[i]
y = (RES_Y) - plot[i]*(RES_Y/MAX_VOLTAGE) - OFFSET
x = i
px = i-1;
py = (RES_Y) - plot[i-1]*(RES_Y/MAX_VOLTAGE) - OFFSET
pygame.draw.line(window, line, (px, py), (x, y))
trig_y = RES_Y - trigger_level * (RES_Y/MAX_VOLTAGE)
pygame.draw.line(window, trig_color, (0, trig_y), (RES_X, trig_y)) - 6). Finalize the oscilloscope by defining the parameters for the oscilloscope's graphical user interface:
##GUI)
font = pygame.font.Font(None, 19)
text_max_voltage = font.render("Max: %f V" % maxv, 1, (255, 255, 255))
text_min_voltage = font.render("Min: %f V" % minv, 1, (255, 255, 255))
text_time_scale = font.render("Timescale: %f s" % time_scale, 1, (255, 255, 255))
text_maxv_Rect = text_max_voltage.get_rect()
text_minv_Rect = text_min_voltage.get_rect()
text_time_scale_Rect = text_time_scale.get_rect()
text_maxv_Rect.x = 10
text_maxv_Rect.y = 10
text_minv_Rect.x = 10
text_minv_Rect.y = 30
text_time_scale_Rect.x = 10
text_time_scale_Rect.y = 50
window.blit(text_max_voltage, text_maxv_Rect)
window.blit(text_min_voltage, text_minv_Rect)
window.blit(text_time_scale, text_time_scale_Rect)
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