Add in XOR of lowest 8 bits of system timer to encourage more randomness of the digits/letters chosen

keyboard/planck/keymaps/cbbrowne/keymap.c

@@ -118,6 +118,8 @@ static uint16_t random_value = 157;
 
 const macro_t *action_get_macro(keyrecord_t *record, uint8_t id, uint8_t opt)
 {
+  uint8_t clockbyte=0;
+  clockbyte = TCNT1 % 256;
   // MACRODOWN only works in this function
   switch(id) {
   case M_LED:
@@ -142,7 +144,12 @@ const macro_t *action_get_macro(keyrecord_t *record, uint8_t id, uint8_t opt)
        a numeric digit chosen at random */
     random_value = ((random_value + randadd) * randmul) % randmod;
     if (record->event.pressed)
-    switch(random_value % 10) {
+
+      /* Here, we mix the LCRNG with low bits from one of the system
+         clocks via XOR in the theory that this may be more random
+         than either separately */ 
+
+      switch ((random_value ^ clockbyte) % 10) {
       case 0:
 	register_code (KC_0);
 	unregister_code (KC_0);
@@ -188,9 +195,12 @@ const macro_t *action_get_macro(keyrecord_t *record, uint8_t id, uint8_t opt)
   case M_RANDLETTER:
     /* Generate, based on random number generator, a keystroke for
        a letter chosen at random */
+    /* Here, we mix the LCRNG with low bits from one of the system
+       clocks via XOR in the theory that this may be more random
+       than either separately */ 
     random_value = ((random_value + randadd) * randmul) % randmod;
     if (record->event.pressed) 
-    switch(random_value % 26) {
+      switch((random_value ^ clockbyte) % 26) {
       case 0:
 	register_code(KC_A);
 	unregister_code(KC_A);