ph testing notes


I have a pH meter (DIY-4502C) hooked up with Raspberry Pi. However, the instruction to calibrate is in Chinese and seems outdated (https://www.diymore.cc/collections/ph-value-detect-sensor/products/diymore-liquid-ph-value-detection-detect-sensor-module-monitoring-control-for-arduino-m).

Does anybody know how to calibrate it for measuring pH4-7? Thanks.

 New contributor


Well, give me the link of the Chinese manual, I can translate it into broken English. 🙂


Do you mean the AT instruction set? Or the hardware setup? I guess they are common to all the real and fake boards. I can do the translation if that is what you need.

The basic Hello test is universal. You say “AT\r\n”, and the Ph Board will return “OK”. The general commands are also universal:

Reset, Current Ph value, Temperature, Threshold, Factory default setting, Current operation mode, …

ph at code

If you wish to translate the names of the pins. Here is one for the J3, J4 pinouts.


You may have already found the location of DS18B20 temperature sensor pin. This is a standard device, so you don’t need to read their instruction.

One other thing is that the vendor recommends to use their CH340 cable. This is important, because other cables using PL23dxx might not work for their board.

You may also find other teething problems. I have a brief suggestion list for the newbies.

  1. Test Rpi 3V3 signals is OK
  2. Test Rpi 3V3 signals converted to 5V logcie is OK.
  3. Test Rpi 3V3/5V0 loopback hardware is OK.
  4. Test Rpi sending string such as “AT/r/n” is OK
  5. Test is CH340 cable is OK

One final reminder to USB CH340 newbies: Remember to disable Serial Console at the Rpi Config Menu:

serial cable disable

And the plug and play, no library required, minimal, complete, verifiable, UART self test/loopabck, repeat send AT/r/n python program.

UART Self Test Program

# uart_test06 tlfong01 2019apr08hkt1603 ***

# Computer = Rpi3B+
# Linux    = $ hostnamectl = raspberrypi Raspbian GNU/Linux 9 (stretch) Linux 4.14.34-v7+ arm 
# Python   = >>> sys.version = 3.5.3 Jan 19 2017

# Test 1   - repeatWriteBytes() - UART port repeatedly send out bytes.  
# Function - Repeat many times sending bytes, pause after each bytes.

# Test 2   - loopBackTest() - UART port send and receive bytes.
# Function - Send one bytes to TX, wait some time (Note 1), then read bytes back from RX. 
# Setup    - Connet Tx pin to Rx pin to form a loop.

# Note 1
# Bolutek BlueTooth BC04 needs at least 10mS to respond

from   time import sleep
import serial

serialPort0 = serial.Serial(port = '/dev/serial0',
        baudrate = 9600,
        parity = serial.PARITY_NONE,
        stopbits = serial.STOPBITS_ONE,
        bytesize = serial.EIGHTBITS,
        timeout= 1)

def setSerialPortBaudRate(serialPort, baudrate):
    serialPort.baudrate = baudrate

def serialPortWriteBytes(serialPort, writeBytes):

def serialPortReadBytes(serialPort, maxBytesLength):
    readBytes = serialPort.read(maxBytesLength)
    return readBytes

def serialPortWriteWaitReadBytes(serialPort, writeBytes, maxBytesLength, waitTime):
    readBytes = serialPortReadBytes(serialPort, maxBytesLength)
    print('        bytes written = ', writeBytes) 
    print('        bytes read    = ', readBytes)
    return readBytes

def repeatWriteBytes(serialPort, writeBytes, pauseTimeBetweenBytes, repeatCount):
    print('       Begin repeatWriteOneByte(), ...')   
    for i in range(repeatCount):
        serialPortWriteBytes(serialPort, writeBytes)                
    print('       End   repeatWriteOneByte().')

def serialPortLoopBack(serialPort, writeBytes, maxBytesLength, waitTime): 
    print('        Begin serialPortLoopBack() [Remember to connect Tx to Rx!] , ...')
    serialPortWriteWaitReadBytes(serialPort, writeBytes, maxBytesLength, waitTime)     
    print('        End   serialPortLoopBack(), ...')

setSerialPortBaudRate(serialPort0, 9600)
#repeatWriteBytes(serialPort0, b'AT\r\n', 0.01, 200000000)
serialPortLoopBack(serialPort0, b'AT\r\n', 32, 0.030)

''' Sample output  tlfong01 2019apr0801
=== RESTART: /home/pi/Python_Programs/test1193/uart_test02_2019apr0801.py ===
        Begin serialPortLoopBack() [Remember to connect Tx to Rx!] , ...
        bytes written =  b'AT\r\n'
        bytes read    =  b'AT\r\n'
        End   serialPortLoopBack(), ...

# End 

Good luck to your project! 🙂


Ph Testing Theory, Ph board pinout translation

Mar 02, 2016, 07:59 pm Last Edit: Mar 02, 2016, 09:26 pm by LeCyb Reason, Arduino Forum

Categories: Uncategorized

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: