// A modbus RTU example that illustrate the library.
// Support for modbus tcp is also included.

#mb_master_ctrl(
       hardware_id := "Local~CB_1241",      
       baud := 9600,                // bits per seconds
       parity := true,              // Enable even parity.
       timeout := T#500ms,            
       mb := #mb );                 // A udt that comes along.

// Instances of device blocks for Siemens PAC3200. (2 devices)
#siemens_PAC3200_instance_1(unit := 1, mb := #mb); 
#siemens_PAC3200_instance_2(unit := 2, mb := #mb); 


// =========================================================
// Device block for: Siemens - PAC3200

"mb_device_header"(common := #common, mb := #mb);

"mb_query"(unit:= #unit,                // The device address.
           fc := #mb.c.read.holding_reg,// Function code 3.
           d_addr := 13,                // Data address.
           d_len := #mb.c.auto_len,     // Automatically calcul. 
           data := #current,            //  
           mb := #mb);                  //- Same udt as above.

"mb_query"(unit:= #unit,                             
           fc := #mb.c.read.holding_reg,
           d_addr := 55,                              
           d_len := #mb.c.auto_len,                   
           data := #frequency,   // "data", can be any datatype, 
           mb := #mb);           //   including arrays and udt's.

"mb_device_footer"(common := #common, mb := #mb);

if #common.out.communication_error then
      #current := 0; 
      #frequency := 0;
end_if ;

// The #common udt contains a log, flags, configuration and 
// internal states. Implementing the device header and footer 
// isn't required, but give many benefits.
// ==============================================================

Key features:

• Makes it easy to split the program in to reusable «device blocks» (interface blocks).
• Device blocks can easily be reused and combined in new programs.
• A clean API, which helps to cut engineering time.
• Reduce idle time, by skipping queries that has led to recurring timeout before. Retries will be done occasionally.
• The library select queries from the device blocks in turn, this prevent one device block from occupying the bus for long periods of time.
• Logging features for development and debugging.

The software is released free under the MIT-license. It can be download at: https://github.com/olab84/rexhip. By reading the «readme» it should be possible to get started. Please don't hesitate to give me feedback on my spare time project. I welcome both posestive and critical thoughts.