How to run tcp slave and serial slave at the same time and share register data 如何同时运行tcp从站和串口从站并共用寄存器数据

[qq547176052]

如何同时运行tcp从站和串口从站并共用寄存器数据
How to run tcp slave and serial slave at the same time and share register data

[alisitsyn]

Hello @qq547176052 ,

Thank you for a very good question on how to share the register data between two slaves and synchronize the data access between them.

For this approach to share the same device memory as registers between the TCP slave instance and the serial slave instance, I can think of several realizations.

Each Modbus instance has its own lock (__lock_t semaphore - mutex object from #include "sys/lock.h" ) sections to protect the data access while mapping. Unfortunately, it is not possible to override this lock mechanism using the existing API.

Approach 1:

• Create and initialize in the application two instances of slave TCP and slave Serial.

• Set up the area descriptors to the same memory in both slaves.

• Use the same lock section for both of your slaves. With the current code, it can be accomplished by overriding the lock_obj(), ulock_obj() functions. The __wrap approach for lock_obj(), ulock_obj() can be used for this. So, both slaves will be able to write and read data from the same memory area, but access will be protected with the critical section, and if one slave accesses the memory from its task, the access from the other slave task will be blocked until the operation is in progress.

Approach 2:

• Create and initialize in your application two instances of slave TCP and Serial.

• Set up the area descriptors to the same memory in both slaves.

• Override the command handlers for commands to map the device data using the same lock critical section in both slaves. So, the critical section based on the same lock object will prevent access to the same mapping area from function handlers of two slave event tasks. The default function handlers call the mapping callbacks, which do the data mapping callback for input registers in the slave. The useful information for the user command handler functions. This can cause some delay processing the Master request by slaves and should be handled accordingly in master increasing the slave response time.

Approach 3:

• Create and initialize in your application two instances of slave TCP and Serial.

• Set up the area descriptors for each slave to use the same register mapping areas into two different memory areas in both slaves.

• Handle synchronization of registers between register areas in two slaves using user application tasks; each handles access to register areas from one slave (serial) to TCP and vice versa. The task waits for notification on register access and copies the written data to another mapping area using the offset. The copy is protected by the critical section with the lock API of the destination object.
  This could be accomplished using queues to synchronize the data between register areas.

Let me know if you have any questions related to above functionality.

To be updated.