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UART handle used in another file as "extern" couldn't be resolved by compiler

Question asked by penguin007 on Nov 18, 2015
Latest reply on Jan 22, 2016 by Kader.M



there are four files I've created: uart.c     uart.h     main.c     main.h. uart.h is included both in uart.c and main.c

my DSP communicates with a device via UART. The processor is BF527, the IDE is CCES

uart functions should be in uart.c, since main.c is already very large. However, there is a problem with the location of  "static ADI_UART_HANDLE hUARTDevice" declaration.  I've tried three ways, only the last one works:


1st way:

If "static ADI_UART_HANDLE hUARTDevice" is declared in uart.c, while declared again as extern "extern static ADI_UART_HANDLE hUARTDevice" in main.c and used in a function in main.c, e.g. adi_uart_Read(), there is an error during compilation:


[Error li1021]  The following symbols referenced in processor 'p0' could not be resolved:

        'hUARTDevice [_hUARTDevice]' referenced from '.\src\main.doj'


Linker finished with 1 error

cc3089: fatal error: Link failed (code:1)

make: *** [main.dxe] Error 1


2nd way:

If "static ADI_UART_HANDLE hUARTDevice" is declared in uart.h. No extern hUARTDevice declared in main.c.Compilation passes. However, there is a real time error is the programm is executed under debug mode:


A non-recoverable error or exception has occurred.

  Description:   Attempted misaligned data memory or data cache access (Exception with EXCAUSE=0x24).

  General Type:  UnhandledException

  Specific Type: DataMisalignedAccessViolation

  Error PC:      0x0180b1d4


A SDRAM is used in my case. May be this error has something to do with SDRAM.


3rd way:

"static ADI_UART_HANDLE hUARTDevice" is declared in uart.c. No extern hUARTDevice declared in main.c. In main.c a wrapper:

UART_Read(void *const pBuffer, uint32_t nBufSize)

is called instead of

adi_uart_Read(ADI_UART_HANDLE const hDevice, void *const pBuffer, uint32_t nBufSize)


Wrapper UART_Read(void *const pBuffer, uint32_t nBufSize) is defined in uart.c.

In this way hUARTDevice is avoided from being used in main.c. But I think this is not a decent way. If many functions which have parameter type ADI_UART_HANDLE must be called in main.c, then lots of wrappers must be written.


I want to use original APIs in main.c, while define uart functions in uart.c. Where should I declare hUARTDevice?