c-code from Pavel for measuring the 1-pps deviation of the 125 MHz AD…

…C clock

src/measure-corr/LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2014-present Pavel Demin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

src/measure-corr/Makefile

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+CFLAGS = -O3 -march=armv7-a -mcpu=cortex-a9 -mtune=cortex-a9 -mfpu=neon -mfloat-abi=hard -ffast-math -fsingle-precision-constant -mvectorize-with-neon-quad
+
+all: measure-corr
+
+measure-corr: measure-corr.c
+	gcc $(CFLAGS) -o $@ $^ -lm -lconfig
+	cp measure-corr ../../
+
+clean:
+	rm measure-corr

src/measure-corr/measure-corr.c

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+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+
+int main(int argc, char *argv[])
+{
+  int fd, i;
+  char *end;
+  volatile void *cfg, *sts;
+  volatile uint32_t *fifo;
+  volatile uint8_t *rst;
+  volatile uint16_t *cntr;
+  long number;
+  uint32_t buffer;
+
+  errno = 0;
+  number = (argc == 2) ? strtol(argv[1], &end, 10) : -1;
+  if(errno != 0 || end == argv[1] || number < 1 || number > 30)
+  {
+    fprintf(stderr, "Usage: measure-corr [1-30]\n");
+    return EXIT_FAILURE;
+  }
+
+  if((fd = open("/dev/mem", O_RDWR)) < 0)
+  {
+    perror("open");
+    return EXIT_FAILURE;
+  }
+
+  sts = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x40000000);
+  cfg = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x40001000);
+  fifo = mmap(NULL, sysconf(_SC_PAGESIZE), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0x4000C000);
+
+  rst = (uint8_t *)(cfg + 3);
+  cntr = (uint16_t *)(sts + 28);
+
+  *rst &= ~1;
+  *rst |= 1;
+
+  sleep(number + 1);
+
+  if(*cntr < number)
+  {
+    fprintf(stderr, "Not enough PPS pulses.\n");
+    return EXIT_FAILURE;
+  }
+
+  buffer = 0;
+
+  for(i = 0; i < number; ++i)
+  {
+    buffer += *fifo + 1;
+  }
+
+  printf("%.2f\n", (125.0e6 * number / buffer - 1.0) * 1.0e6);
+
+  return EXIT_SUCCESS;
+}