Script for Laboratory: Designing embedded ASIPs - CES

Now we will demonstrate how you can create a small application that is using the LCD of the
hardware prototype:
• Create a new subdirectory inside the application directory of your ASIP Meister project
and change into this new directory
• Link to lib_lcd and loadStorByte, but executing:
ln –s /usr/epp/StdLib/lib_lcd.* .
ln –s /usr/epp/StdLib/loadStoreByte.* .
lib_lcd has a dependency to loadStoreByte, that’s why you need both.
• Add a new C file that contains you main method. This main method shall contain the
following code as example:
char* string = “Hello World\r\n”;
t_print(string);
The LCD needs the “\r\n” in the declared string, as it is handling carriage return (\r)
and line feed (\n) independently.
• Compile your project by executing ../mkall.
The resulting program can be simulated with dlxsim or ModelSim or it can be uploaded to the
hardware prototype as it is explained in Chapter 6.3.
After you have once compiled a C-Code that rarely changes with mkall, you can reuse the
created assembly code for future compilations. That will enormously speed up the whole
compilation process. This is especially good for all applications in the StdLib directory. Just
compile them one time with mkall and then copy the created .asm file from the compiler temp
directory to the directory of your other application files, but name it .s instead of .asm. Then
remove the C code (but not the header) to make sure the code does not exist twice (in the C
code and in the Assembly file).
8.5.1 Functions of the LCD library
This chapter will summarize some of the available functions to access the features of the
touch screen LCD of our hardware prototyping board.
int checkbuffer()
Returns the number of available bytes in the send buffer of the LCD. This instruction can be
used to wait for a return value of the LCD. For example when pressing a button on the touch
panel, a value of this button will be written to the LCD send buffer.
int getbytes (char* dest, int bytes_to_read)
Reads a specific number of bytes from the send buffer. With the checkbuffer function you can
test how many bytes are available in the buffer.
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