Bailey O.H.Embedded systems.Desktop integration.2005

Press the Next button and type RSTest as the project name. Select an existing folder to store the project files in. I created a folder named dsPIC\Examples\Chapter9, but you can choose a different directory if you wish.

The dsPIC Peripheral Libraries

Microchip provides a peripheral library that provides “wrapper” functions around dsPIC hardware functions. This library is included with the C30 compiler but can also be downloaded from the Microchip web site. The functions can be called from C or Assembler. We will use the UART, RTC, and SPI libraries. We will implement I2C and the Dallas 1-Wire in software using gen- eral-purpose I/O pins.

MPLAB requires we add the source files for the peripherals to our project. If we don’t, we will get compiler errors since the workbench won’t know where to look for the functions we are using from the UART libraries. In addition, we need to create a source file for testing the serial functions.

The Project Manager window has the project name and a list of file types that can be associated with our project. With the mouse, highlight Source Files, right-click, and select Add Files from the menu. Browse to the pic30_tools\src\peripheral\src\ pmc\uart folder and add OpenUART1.c, CloseUART1.c, and putsUART1.c to the source files. Next, create a new file and name it uart.c, save it to our project directory, and then add it to the source file list. Highlight Linker Scripts in the project view and add pic30_tools\support\gld\p30f2010.gld to the linker script list. This is the default linker script for the dsPIC30F2010 device. Now we are ready to write a short test program. All of our code will be in the uart.c program. Listing 9-1 illustrates how to implement RS-232 in code using the C30 compiler from Microchip.

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}

Note:

To make this work with the dsPICDEM 28 board, pins 2 and 3 on the DB9 must be reversed. This will make the dsPICDEM 28 board the DCE.

Chapter 9

unsigned int slen; int loop;

U1BRG = DIVIDER;

U1_UARTEN = 1;

U1_UTXEN = 1;

slen = strlen(stmsg);

for(loop = 0; (loop < slen); loop++){ U1TXREG = stmsg[loop];

};

while(1){ while(!U1_URXDA); while(!U1_TRMT); U1TXREG = U1RXREG;

};

};

//Length of stmsg

//Array Element Number

//UART BIT RATE BYTE VALUE

//Enable UART 1

//Enable TX 1

//Get String Length

//Loop through string

//Put Array Element in Transmit Register

//While there is no receive data

//and no transmit data

//Echo received data to transmit

There are a couple of differences. Using the C30 compiler we activate and set up both transmit and receive interrupts to clear the interrupt flags, whereas using the dsPICC version we stay in an endless loop echoing characters. Even so, the way dsPICC handles the hardware “wrappers” is slightly different from Microchip’s method. Using dsPICC we directly manipulate the registers through the uppercase names defined in the dspic.h file, while the C30 compiler handles these functions through function calls.

Both methods have advantages and disadvantages. Using C30 the code will be larger, but if Microchip makes changes to the register addresses it will require only a recompile. Using dsPICC will result in smaller code and shorter programs. If you’re an Assembly code person you will probably favor the dsPICC compiler, whereas a C programmer will favor the C30 compiler. Both compilers are excellent products.

The SPI Interface

With the UART interface done, let’s move on to the SPI interface, which is how we will access the non-volatile memory of the DS2404 chip. Again using the Microchip C30 compiler, the code to output SPI data would look similar to Listing 9-3.

Listing 9-3

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}

Now, let’s output that same data using the dsPICC compiler from HI-TECH. In the following listing we are sending the same string a character at a time out the SPI port.

Listing 9-4

/***************************************************************************** htspi - HI-TECH SPI interface for dsPIC. Copyright 2004, Oliver H. Bailey

This program implements the SPI interface using the HI-TECH dsPICC compiler. To use the built-in SPI interface(s) there are two registers and a buffer. The registers are:

*****************************************************************************/

// Alternate method of setting configuration bits. __CONFIG(FOSC, POSC & XTPLL4 & CLKSWDIS & FSCMDIS); __CONFIG(FWDT, WDTDIS);

__CONFIG(FBORPOR, PWRT16 & MCLREN & BORDIS); __CONFIG(FGS, GCPU & GWRU);

__CONFIG(FCOMM, PGEMU);

char stmsg[]={"Hello From Embedded Systems\n\r\0"}; // Test string

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generic routines can be used with the same function calls. The difference is that a separate header file is needed to set up the pins for I2C use. The generic I2C routines can be downloaded from www.wordware.com/files/embsys or www.time-lines.com. Keeping that in mind, the following I2C code will work with either library. The following is a C30 example of how the I2C communications work on the dsPIC.

Listing 9-5

/***************************************************************************** I2C Test program for the Microchip C30 compiler.

Copyright 2004, Oliver H. Bailey

This program implements the I2C interface for the dsPICC using the Microchip C30 Compiler.

****************************************************************************/

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