Add blinky.c. This program runs on the MSS/Linux and accesses the FPGA CAPE apb_blinky

blinky.c

+// blinky.c
+// MUST BE RUN FROM SUDO ./A.OUT
+//
+
+// THIS IS THE BASE ADDRESS OF THE CAPE
+#define CAPE_BASE 0x41000000
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#define PAGE_SIZE (4*1024)
+#define BLOCK_SIZE (4*1024)
+
+int  mem_fd;    // used only in setup_io
+void *cape_map; // used only in setup_io
+volatile unsigned *cape_starting_addr; // set in setup_io
+
+void setup_io();
+
+int main(int argc, char **argv)
+{
+
+  printf("Start of main\n");
+
+  // Set up gpi pointer for direct register access
+  setup_io();
+
+
+  // WRITE TO CAPE's apb_blinky
+  // ONLY OFFSET 1 IS WRITABLE. EACH UNSIGNED IS 4 BYTES, SO IT'S REALLY
+  // BYTE OFFSET 4 IN THE VERILOG.
+
+  for (int ii=0;ii < 8; ii++) {
+    cape_starting_addr[ii] = ii + 0x12345600;
+  }
+
+  // READ FROM CAPE'S APB_BLINKY
+  // EXPECT TO SEE:
+  //   OFFSET[0] = 0X44444444
+  //   OFFSET[1] = 0X12345601 -- THIS IS THE ONLY WRITABLE REGISTER IN APB_BLINKY
+  //   OFFSET[2] = 0X88888888
+  //   OFFSET[3] = 0XCCCCCCCC
+  //   OTHERS    = 0X11223344
+  for (int ii=0;ii < 8; ii++) {
+    printf("cape_starting_addr[%d]=0x%x\n", ii, cape_starting_addr[ii]);
+  }
+
+  // MAKE IT BLINK
+
+  unsigned blink_rate = 500000;  // this is a very fast flickering LED
+  int n;
+  printf("Enter blink speed. 0=off. 100=slow. -1 to quit> ");
+  while (scanf("%d", &n) > 0) {
+    cape_starting_addr[1] = blink_rate*(unsigned)n;
+    printf("blink_rate read back from CAPE=%i\n", cape_starting_addr[1]);
+    printf("Enter blink speed. 0=off. 100=slow. -1 to quit> ");
+  }
+
+  printf("End of main\n");
+
+  return 0;
+} // main
+
+// ============================================================================
+
+// Set up CAPE memory region
+void setup_io()
+{
+  printf("Start of setup_io\n");
+  /* open /dev/mem */
+  if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
+    printf("Error. Could not open /dev/mem. Try running with 'sudo'. \n");
+    exit(-1);
+  }
+
+  /* mmap cape */
+  cape_map = mmap(
+    NULL,             //Any adddress in our space will do
+    BLOCK_SIZE,       //Map length
+    PROT_READ|PROT_WRITE,// Enable reading & writing to mapped memory
+    MAP_SHARED,       //Shared with other processes
+    mem_fd,           //File to map
+    CAPE_BASE         //Offset to CAPE peripheral
+  );
+
+  close(mem_fd); //No need to keep mem_fd open after mmap
+   if (cape_map == MAP_FAILED) {
+     printf("mmap error\n"); 
+     exit(-1);
+  }
+
+  // Always use volatile pointer!
+  cape_starting_addr = (volatile unsigned *)cape_map;
+  printf("End of setup_io\n");
+} // setup_io
+