Here’s a video:
Essentially, the adc reads an analog value and sends it to python. Python connects to a mysql database and adds the data to that. Once the user accesses the php script, a table, containing all of the values, is rendered.
First of all, you’ll need to make a mysql table with the correct specifications:
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CREATE TABLE adc_input_data_10(Sample_Number INT NOT NULL AUTO_INCREMENT PRIMARY KEY, Time VARCHAR(100), Channel_1 VARCHAR(100), Channel_2 VARCHAR(100), Channel_3 VARCHAR(100) ); |
This creates a table that is found in the python script so it is very important that the TABLE values match as well as the column names.
Here’s that python script:
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#!/usr/bin/env python # -*- coding: utf-8 -*- import spidev import time import MySQLdb import sys import RPi.GPIO as GPIO import datetime now = datetime.datetime.now() pin = 26 GPIO.setmode(GPIO.BOARD) GPIO.setup(pin, GPIO.OUT) con = MySQLdb.connect('localhost','adc_user','adc_user_pass','adc_database'); cursor = con.cursor() spi = spidev.SpiDev() spi.open(0, 0) maxcyclenumber = 10 count = 0 def readadc(adcnum): # read SPI data from MCP3008 chip, 8 possible adc's (0 thru 7) if adcnum > 7 or adcnum < 0: return -1 r = spi.xfer2([1, 8 + adcnum << 4, 0]) adcout = ((r[1] & 3) << 8) + r[2] return adcout for _ in range(maxcyclenumber): cursor.execute("INSERT INTO adc_input_data_10(Time,Channel_1,Channel_2,Channel_3) VALUES(%s,'%s','%s','%s')",(datetime.datetime.now().strftime('%b-%d-%I%M%p-%G'),readadc(0),readadc(1),readadc(2)) ) con.commit() #this is important for live updating count = count+1 print count time.sleep (1) if count == maxcyclenumber: GPIO.cleanup() con.close()</pre> |
This reads the values from the adc (it is wired up as seen in this post)
Here’s the php, it reads the values from the adc_input_data_10 table on the adc_database.
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<?php mysql_connect("localhost", "adc_user","adc_user_pass") or die ("Could not connect: " . mysql_error()); mysql_select_db("adc_database"); $result = mysql_query("SELECT * FROM adc_input_data_10"); echo "<table border='1'> <tr> <th>Sample Number</th> <th>Time</th> <th>Channel 1</th> <th>Channel 2</th> <th>Channel 3</th> </tr>"; while($row = mysql_fetch_array($result)){ echo"<tr>"; echo"<td>" . $row['Sample_Number'] . "</td>"; echo"<td>" . $row['Time'] . "</td>"; echo"<td>" . $row['Channel_1'] . "</td>"; echo"<td>" . $row['Channel_2'] . "</td>"; echo"<td>" . $row['Channel_3'] . "</td>"; echo"</tr>"; } echo "</table>"; mysql_close($con); ?> |
This is all very preliminary stuff, and I’ll tighten up the code as time goes on.