Add a way to safely read from controllers

First of all, move some reading utilities into the new `shared`
directory, so controllers can be read by more than one example. Second,
even if we keep the example on `basics/input.s` simple, let's provide a
safe alternative for the other examples.

Signed-off-by: Miquel Sabaté Solà <msabate@suse.com>

2 files changed, 6 insertions, 1 deletions

diff --git a/basics/flicker.s b/basics/flicker.s
index b170d5e..640817a 100644
--- a/basics/flicker.s
+++ b/basics/flicker.s
@@ -36,7 +36,7 @@
 @main_game_loop:
     ;; NOTE: the logic is pretty simply: read the pad, move the player
     ;; accordingly, and apply the flickering effect.
-    jsr Joypad::read
+    jsr joypad_read
     jsr Diskun::update
 
     ;; NOTE: comment this `jsr` out if you want to see what happens if no
diff --git a/basics/input.s b/basics/input.s
index dbb9ee6..6918487 100644
--- a/basics/input.s
+++ b/basics/input.s
@@ -8,6 +8,11 @@
 ;;         we are constantly polling it and filling it, the value will move constantly).
 ;;  - $21: the previous status of the right arrow.
 ;;  - $42: the counter which is incremented on each press of the right arrow button.
+;;
+;; Whenever you are done with this example, hop into the `shared/joypad.s` file,
+;; which brings some other considerations when reading from controllers. That
+;; is, the algorithm shown below is not entirely "safe" due to a hardware bug
+;; which might give unreliable inputs on some spikes.
 ;;;
 
 ;;;