diff --git a/README.md b/README.md
index f708a6b..838eb07 100644
--- a/README.md
+++ b/README.md
@@ -173,14 +173,15 @@ You need **4x M3*12mm screws and 4x M3 hex nuts** to fix all things.
 ### IR Air Tower
 This is not necessary for Chu Pico. But some people may prefer the traditional IR air tower, especially when they're using Chu Pico design for a full-sized controller.
 So hereby I provide the IR air tower design, with a pair of air tower PCBs and the firmware support.
-1. First, you need to order the PCBs, the gerber file is `Production\PCB\chu_air_v*.zip`. It's for both sides of the air tower.
+1. First, you need to order the sensor PCBs, the gerber file is `Production\PCB\chu_air_v*.zip`. It's for both sides of the air tower.
 2. Order the components, they're marked in the schematic. Then solder them to the PCB following the silkscreen.
-3. For left side tower, use J1 to connect to the Raspberry Pi Pico, and for the right side tower, use J2. GPIO 3 -> A, GPIO 4 -> B, GPIO 5 -> C, ADC 0 (GPIO 26) -> Right S, ADC 1 (GPIO 27) -> Left S.  
-  <img src="doc/air_tower_wiring.png" width="50%">
+3. For left side PCB, use J1 to connect to the Raspberry Pi Pico, and for the right side PCB, use J2. GPIO 3 -> A, GPIO 4 -> B, GPIO 5 -> C, ADC 0 (GPIO 26) -> Right S, ADC 1 (GPIO 27) -> Left S.  
+  <img src="doc/air_tower_wiring.png" width="25%"> <img src="doc/chu_air_pcb.png" width="70%">
 
 4. Steps for deployment.
-   * Enable IR air tower in the firmware (command `ir enable`), this will disable ToF.
+   * Enable IR sensor in the firmware (command `ir enable`), this will disable ToF.
    * Enable diagnostics for IR (command `ir diagnostic`).
+   * Orientation of the PCB: for the left side PCB, its J1 is at the lowest, for the right side PCB, its J2 is at the lowest (up-side-down).
    * Place the air towers and watch the output of the diagnostics, higher value means beam is received.
    * Set the baseline after the towers are properly placed (command `ir baseline`).
    * Optionally, set the sensitivity, it's a percentage of expected change (command `ir trigger <1..100>`).
diff --git a/README_CN.md b/README_CN.md
index 2dcc998..cb11cbc 100644
--- a/README_CN.md
+++ b/README_CN.md
@@ -183,12 +183,13 @@ Chu Pico 本身不需要红外空键。但是有些人可能用 Chu Pico 来做
 所以我提供了 IR 空键的设计，包括一对空键 PCB 和对应的固件支持。
 1. 首先，你需要下单 PCB，Gerber 文件在 `Production\PCB\chu_air_v*.zip`。空键的两侧都需要这个 PCB。
 2. 根据原理图里的有标记，购买对应的元器件，然后按照丝印焊接到 PCB 上。
-3. 左侧空键 PCB 使用 J1 连接到 Pi Pico 主控，右侧空键 PCB 使用 J2 连接。GPIO 3 -> A, GPIO 4 -> B, GPIO 5 -> C, ADC 0 (GPIO 26) -> Right S, ADC 1 (GPIO 27) -> Left S。  
-  <img src="doc/air_tower_wiring.png" width="50%">
+3. 左侧传感器 PCB 使用 J1 连接到 Pi Pico 主控，右侧传感器 PCB 使用 J2 连接。GPIO 3 -> A, GPIO 4 -> B, GPIO 5 -> C, ADC 0 (GPIO 26) -> Right S, ADC 1 (GPIO 27) -> Left S。  
+  <img src="doc/air_tower_wiring.png" width="25%"> <img src="doc/chu_air_pcb.png" width="70%">
 
 4. 调试上线的过程如下：
    * 在固件中启用 IR 空键（命令 `ir enable`），它会自动禁用 ToF。
    * 启用 IR 的诊断功能（命令 `ir diagnostic`）。
+   * 注意 PCB 的方向：左侧 PCB，J1 在最下方，右侧 PCB，J2 在最下方（上下颠倒）。
    * 摆放两侧的空键塔，观察诊断输出，数值高代表着对应的红外光线已经对准接收器。
    * 在正确摆放好空键塔后，设置基线（命令 `ir baseline`）。
    * 可选，设置触发灵敏度，它用一个变化的百分比值来表达（命令 `ir trigger <1..100>`）。