Inject additional PIDs with data from external sensors to the existing PIDs from the vehicle OBD adapter about elm327-emulator HOT 3 CLOSED

How can I set values to existing pid with a shellscript or python script?
(not via CMD prompt)?

from elm327-emulator.

Sorry for being late in the answer; my free time is very limited.

put the modified interface to /dev/pts/1

How you do this might not be clear. Notice anyway that if you are using ELM327-emulator as a proxy through its forwarder options, I would not suggest this because that method has been just developed in order to verify and improve the dictionary during the customization phase and not for standard on-line filtering operation.

I don't get what I need to do to modify PID values (or add PIDs) with data from lets say text files containing actual measurement data from external sensors that I added.

I understand that you want to dynamically change the values which are statically predefined in obd_message.py.

I see at least four possibilities.

MODE 1 – using obd_message.py

This method adds a function to obd_message.py to dynamically load a configuration file.

Example.

Create a configuration file (e.g., YAML format):

$ echo -e "---\nINTAKE_PRESSURE: '76'" > /tmp/pid.yaml

Edit obd_message.py and add the following at the top of the file:

import yaml

def load_pid(pid):
    with open('/tmp/pid.yaml', 'rb') as f:
        conf = yaml.load(f.read(), Loader=yaml.BaseLoader)
    return conf[pid]

Take for instance the INTAKE_PRESSURE pid, which returns the following by default.

CMD> test 010B
______Raw command:_______________
'<pos_answer>73</pos_answer>'

______Command output:____________
'41 0B 73 \r\r>'
CMD>

Edit the INTAKE_PRESSURE pid in obd_message.py with the following:

        'INTAKE_PRESSURE': {
            'Request': '^010B' + ELM_FOOTER,
            'Descr': 'Intake Manifold Pressure',
            'ResponseFooter': lambda self, cmd, pid, uc_val: PA(load_pid(pid))
        }, 

Now the 'INTAKE_PRESSURE' returns the value defined in /tmp/pid.yaml by reading the file content each time the pid is requested.

MODE 2 – using batch mode

This method loads predefined parameters via batch mode.

Populate a bash configuration file:

echo "INTAKE_PRESSURE='76'" > /tmp/pid.sh

Develop a batch program reading that file periodically (trivial 1-line example):

while true;do . /tmp/pid.sh; echo "emulator.answer['INTAKE_PRESSURE']='<pos_answer>$INTAKE_PRESSURE</pos_answer>'";sleep 1;done | elm -b /tmp/elm.out

Each second the configuration file is read and the INTAKE_PRESSURE answer is dynamically updated.

MODE 3 – using the python interactive mode

This method performs the interactive loading of parameters via Python Interactive mode.

Create a configuration file (e.g., YAML format):

$ echo -e "---\nINTAKE_PRESSURE: '76'" > /tmp/pid.yaml

Create the following Python program:

from elm import Elm
import time

import yaml

def load_pid(pid):
    with open('/tmp/pid.yaml', 'rb') as f:
        conf = yaml.load(f.read(), Loader=yaml.BaseLoader)
    return conf[pid]

with Elm() as session:
    # interactive monitoring
    pty = session.get_pty()
    print(f"Used port: {pty}")
    while True:
        session.answer['INTAKE_PRESSURE']=(
            '<pos_answer>' +
            load_pid('INTAKE_PRESSURE') +
            '</pos_answer>')
        time.sleep(0.5) # example

This program updates the INTAKE_PRESSURE answer evey second by reading its value from the YAML configuration file.

MODE 4 – developing a task

Create a configuration file (e.g., YAML format):

$ echo -e "---\nINTAKE_PRESSURE: '76'" > /tmp/pid.yaml

Edit the INTAKE_PRESSURE pid in obd_message.py by invoking a task named task_intake_pressure with the following:

        'INTAKE_PRESSURE': {
            'Request': '^010B' + ELM_FOOTER,
            'Descr': 'Intake Manifold Pressure',
            'Task': 'task_intake_pressure'
        }, 

Create a file named "task_intake_pressure.py" in the plugin directory with the following content:

from elm import Tasks
import yaml

def load_pid(pid):
    with open('/tmp/pid.yaml', 'rb') as f:
        conf = yaml.load(f.read(), Loader=yaml.BaseLoader)
    return conf[pid]

class Task(Tasks):
    def run(self, cmd, *_):
        return self.PA(load_pid(self.pid)), Tasks.RETURN.TERMINATE, None

Execution example:

$ elm
2022-01-15 12:45:09,259 - root - INFO -
ELM327 OBD-II adapter emulator v3.0.2 started on pseudo-tty port "/dev/pts/1".
Welcome to the ELM327 OBD-II adapter emulator.
ELM327-emulator is running on /dev/pts/1
Type help or ? to list commands.

CMD> test 010B
______Raw command:_______________
'<pos_answer>76</pos_answer>'

______Command output:____________
'41 0B 76 \r\r>'

CMD> os.system("{ echo '---'; echo \"INTAKE_PRESSURE: '74'\";} > /tmp/pid.yaml")
0

CMD> test 010B
______Raw command:_______________
'<pos_answer>74</pos_answer>'

______Command output:____________
'41 0B 74 \r\r>'

CMD>

By far the task method is the most flexible one.

from elm327-emulator.

By far this is the best answer anyone could get. Maybe the best on the internet.

Thank you so much for your time! I will try that.

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