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  • Author Author: wymand
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HDC1000EVM communications protocol

wymand

Having been in communications since 1962 when NSA recruited me into the Army Security agency and my career after that

as a consultant, WSP communications engineering, WSDOT, and WSCTC consultant, I am particularly interested in how devices talk

So, lacking any reply from TI to questions on protocol, I am looking for myself.

 

The following Program is not intended to be fancy but gives out some communications protocol

that TI has not published yet!  TI has stated their intent to publish the full communications protocol

for the MSP230 communication with the i2c.  As written it works on my RPi B 


import serial

import binascii

#sample program to read Texas Instruments HDC1000EVM

#initialization and open the port

#possible timeout values:

 

 

#    1. None: wait forever, block call

#    2. 0: non-blocking mode, return immediately

#    3. x, x is bigger than 0, float allowed, timeout block call

ser = serial.Serial()

 

 

#ser.port = "/dev/ttyUSB0"

#ser.port = "COM4:"

#ser.port = "/dev/ttyACM1"

ser.port = "/dev/serial/by-path/platform-bcm2708_usb-usb-0:1.2:1.0"

ser.baudrate = 115200

ser.bytesize = serial.EIGHTBITS #number of bits per bytes

ser.parity = serial.PARITY_NONE #set parity check: no parity

ser.stopbits = serial.STOPBITS_ONE #number of stop bits

#ser.timeout = None          #block read

#ser.timeout = 1           #non-block read

ser.timeout = 2              #timeout block read

ser.xonxoff = False     #disable software flow control

ser.rtscts = False     #disable hardware (RTS/CTS) flow control

ser.dsrdtr = False       #disable hardware (DSR/DTR) flow control

ser.writeTimeout = 2     #timeout for write

 

 

try:

    ser.open()

except Exception as e:

    print ("error open serial port: " + str(e))

    exit()

if ser.isOpen():

    try:

        ser.flushInput() #flush input buffer, discarding all its contents

        ser.flushOutput()#flush output buffer, aborting current output

                        #and discard all that is in buffer

        #write data

 

 

        ser.write(serial.to_bytes([0x4C,0x12,0x01,0x00,0x03,0x40,0xFB,0x02,0x7a]))

        response = ser.readline()

        print("read Serial Number MSB = : 0x" + str(binascii.hexlify(response[7])) + str(binascii.hexlify(response[8])))

 

 

        ser.write(serial.to_bytes([0x4C,0x12,0x01,0x00,0x03,0x40,0xFc,0x02,0x11]))

        response = ser.readline()

        print("read Serial Number MID = : 0x" + str(binascii.hexlify(response[7])) + str(binascii.hexlify(response[8])))

 

 

        ser.write(serial.to_bytes([0x4C,0x12,0x01,0x00,0x03,0x40,0xFd,0x02,0x04]))

        response = ser.readline()

        print("read Serial Number LSB = : 0x" + str(binascii.hexlify(response[7])) + str(binascii.hexlify(response[8])))

 

 

        ser.write(serial.to_bytes([0x4C,0x12,0x01,0x00,0x03,0x40,0xFe,0x02,0x3b]))

        response = ser.readline()

        print("read Manufacturer = :" + str(response[7]) + str(response[8]))

 

 

        ser.write(serial.to_bytes([0x4C,0x12,0x01,0x00,0x03,0x40,0xFF,0x02,0x2e]))

        response = ser.readline()

        print("read Device ID = : 0x" + str(binascii.hexlify(response[7])) + str(binascii.hexlify(response[8])))

 

 

        ser.write(serial.to_bytes([0x33]))

        numOfLines = 0

        while True:

            response = ser.readline()

            if (str(response).find(",") == -1):

                print("start data: " + str(response))

            else:

                print("      Temperature: " + str(("{0:.2f}".format(((float(int((str(response).split(',')[0]),16))/float(65536)) * 165) -40)))+ u"\u00B0" + "C")

                print("      Temperature: " + str(("{0:.2f}".format((((((float(int((str(response).split(',')[0]),16))/float(65536)) * 165) -40) * 9) / 5) + 32)))+ u"\u00B0" + "F")

                print("Relative Humidity: " + str(("{0:.2f}".format((float(int((str(response).split(',')[1]),16))/float(65536)) * 100)))+ "%")

            numOfLines = numOfLines + 1

            if (numOfLines > 10):

                #ser.write(bytes(44))

                ser.write(serial.to_bytes([0x34]))

                response = ser.readline()

                print("read data: " + str(response))

                break

                ser.close()

    except Exception as e1:

        print ("error " + str(e1))

    #ser.write(bytes(44))

    ser.write(serial.to_bytes([0x34]))

    response = ser.readline()

    print("last data: " + str(response))

    ser.close()

else:

    print ("cannot open serial port ")

Parents Comment Children
  • in reply to mcb1

    Mark,

    Yes, it is python.  save the program with a name ending in .py I used hdc1000.py

    Then, in a terminal window type python hdc1000.py and it should locate the port

    that the HDC1000EVM is connected on and read the upper registers and 10

    reads of temperature and humidity and then stop the stream, close the port and exit.

     

    It is only intended to prove the HDC1000EVM operated properly on the Raspberry Pi

    and as a clue for others who want to code programs for the device

     

    You will need pyserial.  "apt-get install python-serial" or if you are running python3

    you will have to get python3-serial.

     

    Note I have NOT tried the code on Raspberry Pi Python3, only 2.7 It runs well

    on my Windows8.1 Python33

     

    Let me know of any problems as I would like the code to be compatible.

    On the Raspberry Pi, it locates the device in the /dev/serial folder by name

     

    I haven't moved it around to my other RPi computers yet so the name could change I suppose.

    I do know that if one addresses it by port (/dev/ttyACM0) unplugs it and plugs it back in the

    port may change to /dev/ttyACM1 which is why I used the by name location.

  • in reply to wymand

    Doug

    Thanks for clarifying.

    I don't have the device but thought what you had done, may translate to other things ... hence the clarification.

     

    Cheers

    Mark