ETport templates with multiple devices
There are two ways to use the template system:
- Use one template per device and set the “post_addr_X” and “post_file_X” advanced settings (under System > Advanced Configuration Page -- screenshot below) to the address of the respective devices (the “post_addr_X” variable is a hexadecimal string field corresponding to the two digit hex address of each Modbus device address that is to use that template).
- Combine all devices into one template and address each device/variable within the template by using the $X function (where “X” is the Modbus device address in question). For this to work, the “post_addr_X” setting must be set to all zeros (“0000000000000000000000000000000000000000000000000000000000000000”)
Normally, the template will fail if any device does not respond, or if it responds with an exception (ie: illegal register, etc). However, by using the nofail() function, it will prevent the template from failing, and will fill the variable with a text string which indicates the error.
It is possible to format the template in any format you wish (it is a textfile), however we find that JSON is most common. There are some function parameters which assist to format the output as valid JSON. There is no way to skip reading a missing device, because the only way to identify a missing device is to try to read it in the first place.
Below is an example template and response showing a valid response, exception response, and missing device response, all in one template. (reminder, post_addr_X must be set to all zeros for this to work).
Template:
$nofail(){
"device1_Good_Data": $1.ushort(0x85, format="json")
"device1_Invalid_Register": $1.ushort(0xFFF, format="json")
"device2_Missing": $2.ushort(0x50, format="json")
}
Resulting Post:
{
"device1_Good_Data": 12345
"device1_Invalid_Register": "error: Reading 0fff - 0fff Modbus exception response received: Illegal Data Address (ELKOR_ERROR_MODBUS_EXCEPTION_ILLEGAL_DATA_ADDRESS) [ ModbusExceptionResponseException ]"
"device2_Missing": "error: No MB Response [ TimeoutException ]"
}
Note: you can use a utility like PostMan (https://www.postman.com/) to the /template URL of the ETport (ie: http://192.168.1.100/template) to send the “template” and view the response (screenshot attached). This speeds up development.
