SCPI OPC command not working

Question

I am writing a SCPI script in Python for the Siglent SDS1104X-E. I have been banging my head for a few days trying to get this to work. Below is my main py file:

    
    ################################################################################
    #     Set the Scope IP address and Port number
    ################################################################################
    SCOPE_IP_ADDR = "192.168.1.220"
    SCOPE_IP_PORT = 5025
    ################################################################################
    #     Useful Variables
    ################################################################################
    channel_list = [1, 2, 3, 4] # The values in this list correspond to the 4 channels on the scope.
                                  
    channel_1_dict = {'enable': 'True', 'bandwidth': 'ON', 'coupling': 'D1M',
                      'volt_div': 1, 'volt_offset': 0, 'probe_attenuation': 1}

    sc.config_chan(channel_list[0], channel_1_dict['enable'], channel_1_dict['volt_div'],
               channel_1_dict['volt_offset'], channel_1_dict['coupling'],
               channel_1_dict['bandwidth'], channel_1_dict['probe_attenuation'])

    sc = sds.SDS1104X_Object(SCOPE_IP_ADDR, SCOPE_IP_PORT)
    sc.open_connection()
    sc.reset_inst()
    print(sc.get_id())

My problem is that the reset command (*RST) does not happen fast enough. When configuring multiple channels, it does not always set all of the channels.

Below is a snip from the object that sends the actual commands

    def reset_inst(self):
        self._send_cmd("*RST")

    # helper functions
    def _send_cmd(self, cmd):
        """ send cmd if connected, no resp """
        if self.connection.is_connected:
            self.connection.write(cmd)

    def _send_qry(self, cmd):
        """ send cmd if connected, return resp """
        if self.connection.is_connected:
            self.connection.write(cmd)
            return self.connection.read_raw()
        else:
            return None

The only way I can get this to work is to use the Python "sleep" command after every SCPI command

    time.sleep(3)

The programming manual says to send the *OPC query in order to wait for a command to finish:

I guess I could just put these hard delays everywhere in my script but it seems really clunky and not the best way.

Answer 1

*RST causes the entire scope to reset. It doesn't send a response before the reset, and it can't send one afterwards - the reset causes it to "forget" everything that happened before the reset.

The programming guide tells you when a command will send a response. A command with a response will have a block named "RESPONSE FORMAT" in its description.

What you want to do is to send the "*RST" then periodically ask if the scope is ready to talk to you.

The examples in the guide start with asking for the device identification using the "*IDN?" command.

Send your "*RST" then a short pause (hundred milliseconds or so) then send the "*IDN?" command. Repeat the pause and the "*IDN?" command until you get a good response.

When you look at other commands, take note of whether or not they send a response. If they don't, then you will have to find a different way to see if they succeeded.

For example, the "*RCL" (recall) command doesn't provide a response. If you want to load a particular bunch of settings you have to send the "*RCL" then check the status of the "EXecution error status Register" (command "EXR?") to see if it worked properly.