**0 Preface**
With the widespread use of smartphones and smart TVs, it's becoming increasingly common to use a smartphone's Wi-Fi capabilities for remote control. In China, most urban residents own a smartphone, which they carry with them at all times. However, TV remotes are often left behind or forgotten, leading to inconvenience when trying to turn on the TV or switch channels. By using a smartphone as a remote control, this issue can be effectively resolved. This article explores how to enable Wi-Fi-based remote control of a television using a smartphone.
**1 Hardware Circuit Design**
Although both smartphones and modern TVs are equipped with Wi-Fi, most TVs cannot directly connect to a smartphone’s Wi-Fi network because they lack the capability to run Wi-Fi applications. This means that smartphones cannot communicate with the TV through standard Wi-Fi protocols. However, smartphones can run additional apps designed for Wi-Fi control. Therefore, the key to achieving this control is enabling the TV to receive and interpret Wi-Fi signals from the smartphone.
Most TVs still come with an infrared (IR) remote control function. To adapt this for Wi-Fi control, the IR receiving circuit is replaced with a Wi-Fi-to-TTL control circuit. This allows the smartphone to send control commands over Wi-Fi, which are then converted into IR signals that the TV can understand. The principle remains consistent across different TV models, even though their IR circuits may vary in design.
As an example, this article uses the Hisense LED55K560X3D TV. The interface socket for the IR remote control is defined as shown in Figure 1. The IR signal is sent to the TV, GND is a common ground, STANDBY is the power-on/standby signal, and +5V is the power supply provided by the TV to the IR receiver. Other pins are not used.
Based on this signal definition, a Wi-Fi-to-TTL control circuit was designed, as illustrated in Figure 2. The circuit uses the OCA4004 chip from Qualcomm, which supports IEEE 802.11 a/b/g/n protocols and has an embedded CPU. This makes it simple, reliable, and ideal for secondary development without requiring extra MCUs, ROM, or RAM.
To maintain compatibility with the TV’s original circuitry, the IR remote control interface remains unchanged. The original HX1.25-9P-L-K socket is retained, and the signal pin definitions are not modified. The original STANDBY circuit is also kept intact. However, a resistor R1 is added to the collector of transistor V1, allowing the STANDBY signal to be detected by the OCA4004. The IR receiving and processing circuits are removed and replaced with a Wi-Fi transceiver system centered around the OCA4004. Control signals are processed by the Wi-Fi module, converted into corresponding IR codes, and transmitted via transistor V2 to the TV’s main board, enabling full Wi-Fi-based remote control.
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