From 5357bcfaafbc6e98c93f287085679108f2cd28e3 Mon Sep 17 00:00:00 2001
From: Erick Ahmed <engineering@erickahmed.com>
Date: Fri, 9 Jan 2026 13:48:26 +0100
Subject: [PATCH] Create tap tempo ISR branching logic

---
 src/bpm.inc | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/bpm.inc b/src/bpm.inc
index e89b801..d49b5f7 100644
--- a/src/bpm.inc
+++ b/src/bpm.inc
@@ -2,3 +2,23 @@
     ldi     r20,        \target_high
     ldi     r19,        \target_low
 .endm
+
+ticks_to_bpm:
+    ret
+
+tap_tempo_isr:
+    ; Timer not started yet (first button press after expiration)
+    lds     r16,    timer0_overflow_count
+    cp      r16,    r0
+    breq    start_timer
+
+    ; Timer started
+    ; wait for next press
+    ; better to update at each press, unless expiration
+    rcall   ticks_to_bpm
+
+    reti
+
+start_timer:
+    rcall   timer0_start
+    reti