python - How to change my wxpython program that read and display rain sensor data from mcp3008 to software spi?

Question

I have a completed wxpython code that can read data from rain sensor and convert it from analogue to digital with mcp3008. The problem is the current raspberry pi that I use, already has a 20x4 lcd display that uses pin 24 or GPIO 8 which I need for my rain sensor program. I have read from https://learn.adafruit.com/raspberry-pi-analog-to-digital-converters/mcp3008#software-spi on how to change my spi connection to software spi. Here is my mcp3008 pinout to raspberry pi without lcd display: MCP3008 VDD -> 5V

MCP3008 VREF -> 5V

MCP3008 AGND -> GND

MCP3008 CLK -> pin 23

MCP3008 DOUT -> pin 21

MCP3008 DIN -> pin 19

MCP3008 CS -> pin 24

MCP3008 DGND -> GND

Here is my wxpython code for rain sensor:

import datetime
import spidev
from time import sleep
import os

spi = spidev.SpiDev()
spi.open(0,0)
#global adcOut
adcOut = 0
percent = 0
volts = 0
rain_condition = ""

global current_time
current_time = datetime.datetime.strftime(datetime.datetime.now(), '%d-%m-%y   %H:%M:%S')

try:
    import wx
except ImportError:
    raise ImportError, "The wxPython module is required to run this program."

class RainSensorApp_wx(wx.Frame):
    def __init__(self, parent, id, title):
        wx.Frame.__init__(self, parent, id, size = (700, 300))
        self.SetBackgroundColour(wx.WHITE)
        self.parent = parent
        self.initialize()

    def initialize(self):
        sizer = wx.GridBagSizer()
        font = wx.Font(20, wx.DECORATIVE, wx.ITALIC, wx.NORMAL)
        self.SetFont(font)
        self.label1 = wx.StaticText(self, -1, label = u'Rain Sensor Level: {0:4d}   Percentage: {1:3}%   Voltage: {2}V'.format(adcOut, percent, volts))

        self.label1.SetBackgroundColour(wx.WHITE)
        self.label1.SetForegroundColour(wx.BLACK)
        sizer.Add(self.label1, (1,0), (1,2), wx.EXPAND)

        self.label2 = wx.StaticText(self, -1, label = u'Rain Condition: {}'.format(rain_condition))
        self.label2.SetBackgroundColour(wx.WHITE)
        self.label2.SetForegroundColour(wx.BLACK)
        sizer.Add(self.label2, (2,0), (1,3), wx.EXPAND)

        self.label3 = wx.StaticText(self, -1, label = u'Time Updated: {}'.format(current_time))
        self.label3.SetBackgroundColour(wx.WHITE)
        self.label3.SetForegroundColour(wx.BLACK)
        sizer.Add(self.label3, (3,0), (1,4), wx.EXPAND)

        self.timer = wx.Timer(self)
        self.Bind(wx.EVT_TIMER, self.on_timer, self.timer)
        self.timer.Start(1000)

        self.SetSizer(sizer)
        self.Show(True)

    def on_timer(self,event):
        channel = 0
        if ((channel>7) or (channel<0)):
            return -1

        #r = spi.xfer2([1, (8+channel) << 4, 0])
        #REPLACEMENT
        r = [0]*8
        for i in range(8):
        # The read_adc function will get the value of the specified channel (0-7).
            r[i] = mcp.read_adc(i) 
        #END REPLACEMENT
        adcOut = ((r[1]&3) << 8) + r[2]

        #global adcOut
        percent = int(round(adcOut/10.24))
        volts = ((adcOut/float (1023)) * 5)
        volts = round(volts, 2)

        global current_time
        current_time = datetime.datetime.strftime(datetime.datetime.now(), '%d-%m-%y   %H:%M:%S')
        if adcOut >= 0 and adcOut <= 300:
            self.label1.SetLabel("ADC Output: {0:4d}   Percentage: {1:3}%   Voltage: {2}V".format(adcOut, percent, volts))
            self.label2.SetLabel("Rain Condition: Heavy Rain")
            self.label3.SetLabel("Time Updated: {}".format(current_time))

        elif adcOut >= 0 and adcOut <= 500:
            self.label1.SetLabel("ADC Output: {0:4d}   Percentage: {1:3}%   Voltage: {2}V".format(adcOut, percent, volts))
            self.label2.SetLabel("Rain Condition: Moderate Rain")
            self.label3.SetLabel("Time Updated: {}".format(current_time))

        elif adcOut >= 0 and adcOut <= 700:
            self.label1.SetLabel("ADC Output: {0:4d}   Percentage: {1:3}%   Voltage: {2}V".format(adcOut, percent, volts))
            self.label2.SetLabel("Rain Condition: Light Rain")
            self.label3.SetLabel("Time Updated: {}".format(current_time))

        else:
            self.label1.SetLabel("ADC Output: {0:4d}   Percentage: {1:3}%   Voltage: {2}V".format(adcOut, percent, volts))
            self.label2.SetLabel("Rain Condition: No Rain")
            self.label3.SetLabel("Time Updated: {}".format(current_time))

if __name__ == "__main__":
    Rs = wx.App()
    RainSensorApp_wx(None, -1, 'Rain Sensor Monitor')
    Rs.MainLoop()

Here is the example code from the AdaFruit_MCP3008 after I followed the steps on the web given to install the library:

# Simple example of reading the MCP3008 analog input channels and printing
# them all out.
# Author: Tony DiCola
# License: Public Domain
import time

# Import SPI library (for hardware SPI) and MCP3008 library.
import Adafruit_GPIO.SPI as SPI
import Adafruit_MCP3008


# Software SPI configuration:
CLK  = 18
MISO = 23
MOSI = 24
CS   = 25
mcp = Adafruit_MCP3008.MCP3008(clk=CLK, cs=CS, miso=MISO, mosi=MOSI)

# Hardware SPI configuration:
# SPI_PORT   = 0
# SPI_DEVICE = 0
# mcp = Adafruit_MCP3008.MCP3008(spi=SPI.SpiDev(SPI_PORT, SPI_DEVICE))


print('Reading MCP3008 values, press Ctrl-C to quit...')
# Print nice channel column headers.
print('| {0:>4} | {1:>4} | {2:>4} | {3:>4} | {4:>4} | {5:>4} | {6:>4} |     {7:>4} |'.format(*range(8)))
print('-' * 57)
# Main program loop.
while True:
    # Read all the ADC channel values in a list.
    values = [0]*8
    for i in range(8):
        # The read_adc function will get the value of the specified channel (0-7).
        values[i] = mcp.read_adc(i)
    # Print the ADC values.
    print('| {0:>4} | {1:>4} | {2:>4} | {3:>4} | {4:>4} | {5:>4} | {6:>4} | {7:>4} |'.format(*values))
    # Pause for half a second.
    time.sleep(0.5)

Can somebody help me on how to change my program to read data with the software spi, as I need to change the Software spi configuration to:

CLK = 23

MISO = 21

MOSI = 19

CS = 29

Answer 1

Without knowing what Adafruit_MCP3008 is returning and without access to the hardware to be able to test it, I suspect that your existing line:

r = spi.xfer2([1, (8+channel) << 4, 0])

should be replaced by:

r = [0]*8
for i in range(8):
    # The read_adc function will get the value of the specified channel (0-7).
    r[i] = mcp.read_adc(i) 

The only way to know for sure would be to print out r as it is in your current set up and then do the same for the new one, to see if there are any differences and what they are.