fixed a bug... :/

in the while loop in main() that busywaits until we can scan again, the
compiler was optimizing out the function call, it seems like, when i
wrote `(uint8_t)timer__get_milliseconds()`; if i cast the whole
expression (not just the function) to `(volatile uint8_t)`, or if i just
didn't cast anything at all, it worked.  not sure why the compiler would
optimize the function call out like that though, even if it was cast...
this happened when i put it in a for loop too.  i need to research it
just a little more, and write a warning about it in the timer
documentation.

firmware/keyboard/ergodox/led.c

@@ -73,17 +73,17 @@ bool kb__led__read(uint8_t led) {
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 
 void kb__led__all_on(void) {
-    for(int8_t i=1; i<=3; i++)
+    for(uint8_t i=1; i<=3; i++)
         kb__led__on(i);
 }
 
 void kb__led__all_off(void) {
-    for(int8_t i=1; i<=3; i++)
+    for(uint8_t i=1; i<=3; i++)
         kb__led__off(i);
 }
 
 void kb__led__all_set(float n) {
-    for(int8_t i=1; i<=3; i++)
+    for(uint8_t i=1; i<=3; i++)
         kb__led__set(i, n);
 }
 

firmware/lib/timer.h

@@ -8,8 +8,6 @@
  * Timer interface
  *
  * Prefix: `timer__`
- *
- * `timer__init()` is meant to be called once, on startup, by `main()`
  */
 
 
@@ -19,9 +17,16 @@
 // ----------------------------------------------------------------------------
 
 
-void timer__init(void);
+uint8_t timer__init(void);
 /**                                           functions/timer__init/description
  * Initialize the timer
+ *
+ * Returns:
+ * - success: `0`
+ * - failure: [other]
+ *
+ * Notes:
+ * - Should be called exactly once by `main()` before entering the run loop.
  */
 
 uint32_t timer__get_milliseconds(void);

firmware/lib/timer/atmega32u4.c

@@ -22,11 +22,13 @@ static volatile uint32_t _milliseconds;
 
 // ----------------------------------------------------------------------------
 
-void timer__init(void) {
+uint8_t timer__init(void) {
     TCCR0A = 0b10000010;
     TCCR0B = 0b00000011;
     TIMSK0 = 0b00000010;
     OCR0A  = 250;
+
+    return 0;  // success
 }
 
 uint32_t timer__get_milliseconds(void) {

firmware/main.c

@@ -11,7 +11,6 @@
 
 #include <stdbool.h>
 #include <stdint.h>
-#include <util/delay.h>
 #include "../firmware/keyboard.h"
 #include "../firmware/lib/timer.h"
 #include "../firmware/lib/usb.h"
@@ -68,7 +67,7 @@ int main(void) {
 
     static uint8_t time_scan_started;
 
-    kb__init();     // initialize hardware (besides USB and timer)
+    kb__init();  // initialize hardware (besides USB and timer)
 
     kb__led__state__power_on();
 
@@ -80,9 +79,16 @@ int main(void) {
 
     kb__led__state__ready();
 
-    time_scan_started  // first iteration, scan immediately
-        = (uint8_t)timer__get_milliseconds() - OPT__DEBOUNCE_TIME;
+    time_scan_started  // on the first iteration, scan immediately
+        = timer__get_milliseconds() - OPT__DEBOUNCE_TIME;
 
+    // TODO
+    // - test the scan rate, to make sure it's what we want
+    // - write a nice note about not casting `timer__get_milliseconds()` inside
+    //   while loops... or maybe write a `timer__diff_with_now()` or something
+    //   function
+    // - look at the generated asm for these things, maybe, to see what's going
+    // on
     for(;;) {
         temp = is_pressed;
         is_pressed = was_pressed;
@@ -91,7 +97,7 @@ int main(void) {
         // delay if necessary, then rescan
         // - add 1 to `OPT__DEBOUNCE_TIME` in case `time_scan_started` caught
         //   the tail end of the millisecond it recorded
-        while( (uint8_t)timer__get_milliseconds() - time_scan_started
+        while( timer__get_milliseconds() - time_scan_started
                < OPT__DEBOUNCE_TIME + 1 );
         time_scan_started = timer__get_milliseconds();
         kb__update_matrix(*is_pressed);