The application appl/goal_mb/01_simple_io demonstrates the usage of the GOAL Modbus Stack. It defines data regions for specific data types, opens up a Modbus instance and creates objects.

Footprint

The application uses with enabled logging at the platform STM32F429_nucleo about 52 kB of RAM and 240 kB of FLASH.

Data Regions

The application uses the function goal_mbCfgDataRegionDefine to define accessable regions for specific data types.

Data Type	Region

Data Type	Region
GOAL_MB_DATA_COIL	1000 to 1049
GOAL_MB_DATA_HOLD_REG	3000 to 3049

This function only restricts regions used by Coils and Holding Registers. Other Data Types must be handled by the application itself.

Data Objects

The application creates objects as following:

Data Type	Name(s)	Address(es)

Data Type	Name(s)	Address(es)
Coil	APPL_COIL_1	1000
Coil	APPL_COIL_2	1001
Discrete Input	APPL_DISC_INPUT_1 to APPL_DISC_INPUT_10	2000 to 2009
Holding Register	APPL_HOLD_REG_1	3000
Holding Register	APPL_HOLD_REG_2	3001
Input Register	APPL_INPUT_REG_1 to APPL_INPUT_RES_10	3050 to 3059

Application Logic

The application provides a generic callback handler, which handles events like received read-requests or write-requests and connection-related events. Handles callback IDs are the following:

GOAL_MB_CB_ID_APPL_READY
GOAL_MB_CB_ID_DATA_READ
- the called function appl_readRequestProcess provides the discrete inputs, input- and holding registers and returns random values and LED states to the requested objects.
GOAL_MB_CB_ID_DATA_WRITE
- the called function appl_writeRequestProcess handles write requests for a holding register, setting the written value to target specific LED registers.
GOAL_MB_CB_ID_CONNECT_REQUEST
GOAL_MB_CB_ID_CONNECT_RELEASE
GOAL_MB_CB_ID_LED_CHANGED

Available Callback IDs are listed here.

There is also an application loop implemented, which mirrors application coils every 100 ms.