Aftermarket head units, like those from Joying, often utilize Key1 and Key2 wires for integrating steering wheel controls (SWC). These wires allow drivers to retain the convenience of controlling audio, calls, and other functions without removing their hands from the steering wheel. Understanding how these Key1 Key2 Wires function is crucial for a successful SWC integration.
Deciphering Key1 Key2 Wiring and Resistance
Key1 and Key2 inputs on Joying head units are resistance-based. Each button on the steering wheel corresponds to a specific resistance value. When a button is pressed, the corresponding resistance is measured by the head unit, triggering the assigned function.
The typical wiring setup involves a resistor in series with each steering wheel button. These button/resistor pairs are wired in parallel with each other. One side of this parallel circuit connects to ground, while the other connects to the Key1 input. Key2 functions identically to Key1, providing a second input for an additional set of buttons, if needed. This allows for a wider range of control options from the steering wheel. There might also be an additional resistor in the parallel circuit.
(Example wiring diagram for Key1 and Key2. Replace with actual image from original article if available and relevant.)
One user on the Joying forum successfully used a circuit with a 75-ohm base resistance and 10-ohm increments for each subsequent button. Another user with a specific vehicle found that their OEM steering wheel controls used a 4.7kOhm resistance with no buttons pressed and different resistances for each of the six buttons. Importantly, this user highlighted that the system measures resistance to ground, not between Key1 and Key2. Connecting the SWC negative wire to ground allowed for proper functionality.
Practical Application and ADC Input
The Key1 and Key2 inputs act as analog-to-digital converters (ADCs). They measure the resistance and convert it to a numerical value, typically ranging from 0 to 255. This value is then interpreted by the head unit to determine which button was pressed. Accessing the steering wheel control settings in the head unit allows for customization and mapping of these buttons to specific functions.
(Example of steering wheel control settings interface in a Joying head unit. Replace with actual image from original article if available and relevant.)
In the Joying car settings menu under steering controls, there are usually two rows of assignable key functions. The top row often displays a fluctuating number (e.g., 254~255) above each button, indicating the ADC reading. The functionality of the second row without numbers may vary depending on the specific head unit model and firmware.
Conclusion: Successfully Integrating Steering Wheel Controls
Successfully integrating steering wheel controls with a Joying head unit relies on understanding the resistance-based nature of the Key1 Key2 inputs. Experimentation and referencing online forums, like the Joying forum, can help determine the specific resistance values needed for your particular vehicle and head unit. By understanding how these inputs function, drivers can enjoy a seamless and integrated driving experience.
