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Compiler/TM4C1237H6PZ: Standard IO Functions in Debug Mode

Part Number: TM4C1237H6PZ

Tool/software: TI C/C++ Compiler

Hi Support,

I need help in having the standard I/O functions working in debug mode.
The diagnose I was able to do is that __CIOBUF_ is not cleared (read by the debugger?) after __TI_writemsghas been called, so that __TI_readmsgreturns the value 499 that obviously makes the system jump into an invalid portion of the buffer.
The CIO console does not appear and a Fault condition is issued with a call to FaultISR.

Printf support is set to full. heap size is set to 2kBytes, CIO functions use is enabled. What am I missing?

Project 4555290 is instead woking, opening the CIO console and displaying the fabulous "Hello world!" string.
I tried to check for differences in the projects properties, but was not able to find any (to me) meaningful difference.

Could you please help me?

Thanks and regards,


  • It is true that CIOBUF is not cleared between CIO calls; this is not by itself indicative of a problem.
    Please make sure you have read
    Make sure CIOBUF is in read-write memory, not FLASH
    It may be that 2k heap is not enough. Try increasing the size of the heap.
    Try giving stdio its own, non-dynamic buffer by using setvbuf
    What function are you calling to perform CIO? I assume it's printf? Try puts instead
    Did you alter the RTS library in any way?