From 89aa777d5c41c9b0b6e97e0ae41832c94c00a5ab Mon Sep 17 00:00:00 2001
From: SkyLi <SkyLiA7Mr@gmail.com>
Date: Sun, 7 Jun 2026 15:06:58 +0800
Subject: [PATCH] docs: add 0xA9 feedforward frame to host comm guide

---
 docs/host_comm_guide.md | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/docs/host_comm_guide.md b/docs/host_comm_guide.md
index e854dfa..330bc55 100644
--- a/docs/host_comm_guide.md
+++ b/docs/host_comm_guide.md
@@ -19,6 +19,35 @@
 | 0xA6 | 10 | 手动控制数据 |
 | 0xA7 | 3 | 命令 |
 | 0xA8 | 50 | 调试调参数据 |
+| 0xA9 | 6 | 前馈输入 |
+
+---
+
+## 5. 前馈输入帧 0xA9 (6 字节)
+
+**用途**: 下发前馈输入值到 yaw 电机前馈控制器，在自动和手动模式下均可生效。
+
+```
+[SOF:0xA9][feedforward:4][checksum:1]
+```
+
+| 偏移 | 长度 | 类型 | 含义 |
+|---|---|---|---|
+| 0 | 1 | uint8 | 帧头 0xA9 |
+| 1 | 4 | float | 前馈输入值 |
+| 5 | 1 | uint8 | checksum |
+
+**Python 写入示例**:
+
+```python
+def send_feedforward(ser, feedforward: float):
+    data = bytearray()
+    data.append(0xA9)
+    data.extend(struct.pack('<f', feedforward))
+    checksum = sum(data) & 0xFF
+    data.append(checksum)
+    ser.write(data)
+```
 
 ---