rref requestable via mqtt

test/.gitignore

@@ -1,4 +1,5 @@
 airspeed
 heading
 mqtt
-mqtt.h
+mqtt.h
+strtoint

test/strtoint.c

@@ -0,0 +1,44 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+
+int *strtoint(char *in, size_t start, size_t n)
+{
+    int *ret = malloc(sizeof(int));
+    *ret = 0;
+    int offset = start + n - 1;
+
+    if (offset < 0)
+    {
+        return NULL;
+    }
+
+    for (int i = 0; i < n; i++) {
+        int position = offset - i;
+        printf("foo: %c\n", in[position]);
+        if (in[position] >= '0' && in[position] <= '9')
+        {
+            *ret += (in[position] - '0') * pow(10, i);
+        }
+        else
+        {
+            return NULL;
+        }
+    }
+
+    return ret;
+}
+
+int main()
+{
+    char *in = "abcd123";
+    int *ret = strtoint(in, 4, 3);
+    if (ret != NULL)
+    {
+        printf("%s | %d\n", in, *ret);
+    }
+    else
+    {
+        printf("ret is NULL\n");
+    }
+}