Introduction

My name is Ryosuke Kamei and I am an IT consultant based on the idea of "gentle IT"! Currently, in my work, I am doing upstream processes focusing on requirements analysis and requirements definition, but I also write programs! As part of our friendly IT activities, we will introduce "Raspberry Pi 3" (commonly known as Raspberry Pi), which has the philosophy of "providing inexpensive PCs that can be programmed for education"!

This time, we will detect the analog signal converted by the A / D converter! [Razpai Magazine-June 2016 Special Feature 1 Akiba's Popular Parts Wiring Diagram Best 17 11 Can Read Analog Signals](https://www.amazon.co.jp/ Razpai Magazine-June 2016 Issue-Nikkei BP PC Best Mook -? Nikkei Linux-ebook / dp / B01EH2RX42 / ref = as_li_ss_tl ie = UTF8 & dpID = 61P3o6Agz + L & dpSrc = sims & preST = OU09__BG0,0,0,0_FMpng_AC_UL160_SR120,160 & psc = 1 & refRID = 31SKG5E0DGKBSF9BWNGV & linkCode = ll1 & tag = sr2smail-22 & linkId = 18fd04738627edef8d6fffd6c9b8f9c2) Is referred to.

procedure

Wiring
Program adc.py
Run the program

1. Wiring

The wiring diagram is [Razpai Magazine-June 2016 Issue Special Feature 1 Akiba's Popular Parts Wiring Diagram Best 17 11 Can Read Analog Signals](https://www.amazon.co.jp/ Razpai Magazine-2016 6 Monthly issue-Nikkei BP PC Best Mook-Nikkei Linux-ebook / dp / B01EH2RX42 / ref = as_li_ss_tl? 22 & linkId = 18fd04738627edef8d6fffd6c9b8f9c2) As it is.

If you get an image like this, referring to the picture of the circuit Raspberry Pi 3でpythonを使い::Dコンバーターでアナログ信号を検出する！回路.jpg

I also made a video

Text version

From the Raspberry Pi side

--Raspberry Pi Pin 1 (3.3V) --AD Converter 8 Vdd --Semi-fixed resistor left side --Raspberry Pi 19th pin (MOSI) --AD converter 5 MOSI --Raspberry Pi 21st pin (MISO) --AD converter 6 MISO --Raspberry Pi 23rd pin (SCLK) --AD converter 7 CLK --Raspberry Pi 24th pin (CE0) --AD converter 1 CS --Raspberry Pi 6th pin (GND) --AD converter 4 Vss --Semi-fixed resistor right side

From AD converter (difference only)

--AD converter CH0 --Semi-fixed resistor center

2. Program adc.py

Program is also [Razpai Magazine-June 2016 Issue Special Feature 1 Akiba's Popular Parts Wiring Diagram Best 17 11 Can Read Analog Signals](https://www.amazon.co.jp/ Razpai Magazine-June 2016 Issue -Nikkei BP PC Best Mook-Nikkei Linux-ebook / dp / B01EH2RX42 / ref = as_li_ss_tl? Ie = UTF8 & dpID = 61P3o6Agz + L & dpSrc = sims & preST = _OU09__BG0,0,0,0_FMpng_AC_UL160_SR120,0_FMpng_AC_UL160_SR120 It is based on 18fd04738627edef8d6fffd6c9b8f9c2).

The source is uploaded to GitHub, so please use it as you like.

`Clone with git`


$ git clone https://github.com/RyosukeKamei/raspberrypi3.git

`adc.py`


#Library to control GPIO
import wiringpi
#Timer library
import time

#Specify the channel to which MCP3002 (semi-fixed resistor) is connected
SPI_CH = 0

#Specify the analog input channel of the MCP3002 (semi-fixed resistor) to be read
READ_CH = 0

#SPI initialization
wiringpi.wiringPiSPISetup( SPI_CH, 1000000 )

while True:
    #Create data to send to MCP3002 (semi-fixed resistor)
    buffer = 0x6800 | ( 0x1800 * READ_CH )
    buffer = buffer.to_bytes( 2, byteorder='big' )
    
    #Get the value of CH0 using SPI
    wiringpi.wiringPiSPIDataRW( SPI_CH, buffer )
    #The values are sent in 2 bytes, so combine them into one value.
    ch0_value = ( buffer[0] * 256 + buffer[1] ) & 0x3ff
    #Convert value to voltage
    volt = ch0_value * 3.3 / 1023
    # 0.Every 5 seconds
    time.sleep(0.5)
    print ("value:" , ch0_value , "Voltage:", volt , "V")