Segault on Python i2c call



  • Hello,

    I'm rewriting some code that reads an I2C current sensor. In my rewrite I run into a segfault on an i2c write. The code in question is:

    def pecmac():
        """
        Support for the Control Everything current sensor. Code has been tested with the 70A/3 channel model
        :return:
        """
        logging.debug('...... i2c create')
        i2c = onionI2C.OnionI2C(0x01)
    
        #set the verbosity
        logging.debug('...... i2c set verbosity')
        i2c.setVerbosity(0x01)
    
        command2 = [
            0x6A,
            0x02,
            0x00,
            0x00,
            0x00,
            0x00,
            0xFE,
        ]
    
        logging.debug('...... i2c command2')
        i2c.writeBytes(0x2A, 0x92, command2)
    

    The first time I run this code, all is well. But on the second run (after a 60s sleep inside the loop) I end up with a segfault.

    The output I get (with the actual data collection output as well is:

    20180203 21:31:41 Detected our hostname as [OMEGA-F6BB]
    20180203 21:31:41 Creating database connection
    20180203 21:31:41 .. Done
    20180203 21:31:41 Reading sensor data
    20180203 21:31:41 .. Reading data from sensor PECMAC
    20180203 21:31:41 ...... i2c create
    20180203 21:31:41 ...... i2c command2
    20180203 21:31:42 ...... i2c readbytes
    20180203 21:31:42 Type of Sensor: 4 | Maximum Current : 70A | No. of Channels: 3
    20180203 21:31:42 Channel no: 1 | Current Value: 0.376A
    20180203 21:31:42 Channel no: 2 | Current Value: 0.000A
    20180203 21:31:42 Channel no: 3 | Current Value: 0.000A
    [{'Timestamp': 1517722302698L, 'Sensor': 'pecmac', 'Value': 0.376, 'Measurement': 'ch1_current'}, {'Timestamp': 1517722302698L, 'Sensor': 'pecmac', 'Value': 0.0, 'Measurement': 'ch2_current'}, {'Timestamp': 1517722302698L, 'Sensor': 'pecmac', 'Value': 0.0, 'Measurement': 'ch3_current'}]
    20180203 21:31:42 Processing the sensor data
    20180203 21:31:42 .. Sending data to UBIDOTS
    20180203 21:31:42 .... Checking if Ubidots is Online
    20180203 21:31:43 .. Submitting data to Ubidots
    20180203 21:31:43 {"ch1_current": {"timestamp": 1517722302698, "value": 0.376}}
    20180203 21:31:44 {"ch2_current": {"timestamp": 1517722302698, "value": 0.0}}
    20180203 21:31:44 {"ch3_current": {"timestamp": 1517722302698, "value": 0.0}}
    20180203 21:32:44 .. Reading data from sensor PECMAC
    20180203 21:32:44 ...... i2c create
    20180203 21:32:44 ...... i2c command2
    Segmentation fault
    

    Logread shows:

    Sat Feb  3 21:32:44 2018 kern.info kernel: [ 1251.955047] do_page_fault(): sending SIGSEGV to python for invalid write access to 00000000
    Sat Feb  3 21:32:44 2018 kern.info kernel: [ 1251.963673] epc = 77ce6864 in libc.so[77cbe000+92000]
    Sat Feb  3 21:32:44 2018 kern.info kernel: [ 1251.968855] ra  = 779eac69 in libonioni2c.so[779ea000+11000]
    

    Please note this is with some extra kernel modules to deal with I2C issues as per https://community.onion.io/topic/2312/i2c-detect-slave-method

    tx
    Bas


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