First, we need to know the exact physical addresses of both LEDs. From EP93xx User's Guide we see that both LEDs are connected to PortE bits 1 and 0 (pp. 28-9 - 28-10). PortE Data Register is mapped to 0x80840020 and PortE Data Direction Register to 0x80840024 respectively. Now we are ready to write a really simple program that toggles the two LEDs continuously:
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int main() {
unsigned char *portE_DDR;
unsigned char *portE_DR;
unsigned long delay = 1000000L;
unsigned long i;
int x = 0;
portE_DDR = (unsigned char *) 0x80840024;
portE_DR = (unsigned char *)0x80840020;
//printf("address is -> %0X",portE_DDR);
//return 1;
*portE_DDR |= 0x03;
*portE_DR = 0x03;
for(;;) {
for(i=0; i<delay; i++) { x = 123 + 542 * 123; };
*portE_DR = 0x02;
for(i=0; i<delay; i++) { x = 123 + 542 * 123; };
*portE_DR = 0x01;
}
return 0;
}
To build the program above we will use GNUARM toolchain. The exact commands used to compile and link the binary are given bellow:
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# arm-elf-gcc -O0 -c leds.c
# arm-elf-ld -e main -o leds.elf leds.o
This will produce leds.elf executable with the following file type:
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# file leds.elf
leds.exe: ELF 32-bit LSB executable, ARM, version 1, statically linked, not stripped
Now we are ready to load and execute the binary on the EP9302 board. To do this we will use the capabilities of the RedBoot to load network files (using FTP, TFTP, or HTTP). Once we have an open RedBoot shell with correct TCP/IP configurations all we need to do is to execute the following commands (assuming that leds.elf binary file is available through URL: http://dsnet.tu-plovdiv.bg/leds.elf).
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RedBoot> load -h 192.168.32.51 -m http -b 0x00800000 /leds.elf
RedBoot> go 0x00800000
That's it. You should now see how both LEDs sequentially changes their state from on to off.
TODO: How to build binaries that returns control to RedBoot when finished.
