How to read diagnostic messages from foreign implement connected to network

[oleszczyk]

I have created my own Task Controller server instance for communicating with Gaspardo corn seeder ISOBUS controller unit for automatic section control. I am testing Gaspardo controller on my desk (disconnected from all real machinery: sections, vacuum and speed sensors) powered by my laboratory power supply and simply connected to my device with CAN lines.

In general it works well:

• I can talk with Gaspardo ISOBUS Task Controller client,
• I parse implement DDOP and can see supported DDIs,
• I can finally even modify value for one of DDI: turning on SectionControlState (0x00A0),

But I am unable to actually control sections - I constantly read value 0xfffff000 from DDI ActualCondensedWorkState1_16 (0x00A) and setting SetpointCondensedWorkState1_16 (0x0122):

send_set_value(controlFunction,
               static_cast<std::uint16_t>(isobus::DataDescriptionIndex::SetpointCondensedWorkState1_16),
               80, 0xFFFFF001);

does not change anything (still value 0xfffff000 on ActualCondensedWorkState1_16).

My assumption is that maybe seeder controller detects that it is disconnected from physical machinery so it does not reacts on my tries of section controlling (which is kind of logical). If so then I assume it would broadcast some messages/errors via ISOBUS diagnostic protocol to the network informing it detects some hardware issues.

I have seen that AgIsoStack++ has support for diagnostic protocol but as far as I understand implementation (and available example) it covers a case that I can use it for transmitting/broadcasting diagnostic messages from my own node to the network.

My question: is it possible to read/fetch/parse diagnostic messages sent by foreign implement connected to the network? In my case I would like to print diagnostic from connected Gaspardo ISOBUS unit.