From d4fbc17d4362b8c9927a3fc01da770b97259f046 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sybren=20A=2E=20St=C3=BCvel?= <sybren@stuvel.eu>
Date: Sat, 14 Mar 2026 20:15:24 +0100
Subject: [PATCH] Cut up log lines into 20-byte BLE packets

---
 src/helpers/esp32/BLELogInterface.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/helpers/esp32/BLELogInterface.h b/src/helpers/esp32/BLELogInterface.h
index db94de63..30442ccc 100644
--- a/src/helpers/esp32/BLELogInterface.h
+++ b/src/helpers/esp32/BLELogInterface.h
@@ -31,8 +31,18 @@ class BLELogInterface : public Print, BLEServerCallbacks {
 
   void flushLine() {
     if (_line_len > 0 && _connected) {
-      _tx_char->setValue((uint8_t*)_line_buf, _line_len);
-      _tx_char->notify();
+      // BLE notifications are capped at ATT_MTU-3 bytes; MTU negotiation is not
+      // guaranteed, so always chunk at 20 bytes (the safe minimum) to ensure the
+      // full line is delivered regardless of the negotiated MTU.
+      const int CHUNK = 20;
+      int offset = 0;
+      while (offset < _line_len) {
+        int n = _line_len - offset;
+        if (n > CHUNK) n = CHUNK;
+        _tx_char->setValue((uint8_t*)_line_buf + offset, n);
+        _tx_char->notify();
+        offset += n;
+      }
     }
     _line_len = 0;
   }