Question

I have Dallas Sensors connected to FMC640 device and configured to send Temperatures and IDs in AVL packet.
When I set IO global settings to "Don't send" I encounter that Dallas Temperature data are not available.
But why 1-wire data are not available?
I set device sleep mode to "1" to avoid device sleep.
I assume that if there is sensors connection problem then device will send value 3000, but it not sending at all.

What about IO global setting in oder to 1-wire:
- DontSend - but I need info about eventual connection problem
- Send Zero - when it sends zero and when 3000 connection error?
- Send Last Known Value - not acceptable it will create not existing data in system
- Send 0xFF - the same as zeros, what does mean 0xFF it is connection error or what?

Answer 1

Hello,
If you set IO global settings to "Don't send", the Dallas Temperature data will not be available in the AVL packet. To receive information about any connection problems, you can set the IO global setting to "Send zero". The device will send a value of zero when there is a connection problem. A value of 3000 indicates a communication error. "Send Last Known Value" is not recommended, as it can create false data. "Send 0xFF" is not a valid option for 1-wire sensors.

MyMorri

Comments

But when device send zero value for dallas sensor I could not differentiate it with real measured 0.0^C value.
So, more convinient way could be 0xFF because this value is above valid range for DS18B20.