Segault on Python i2c call

Bas Rijniersce

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