Fuel Tank Trainer Calibration Manual

Part 1: Quick Start Guide

1. Wi-Fi Connection & Access

The system hosts its own wireless network to provide a visual calibration dashboard. Please follow these steps to connect:

• Power Up: Supply power to the Fuel Tank Trainer.
• Connect Wi-Fi: Open the Wi-Fi settings on your device, search for, and connect to the SSID: Fuel_Tank_Trainer.
• Password: Enter the password: 12345678
• Access Dashboard: Open any web browser and enter the following IP address in the URL bar: 192.168.4.1.

2. Startup Sweep Self-Test

• Every time the system is powered on, it automatically enters a 5-second gauge sweep mode. All connected physical gauge needles will smoothly sweep from their minimum position (Empty) to their maximum position (Full) and drop back down.
• Sweep Test can also trigger manually in the calibration dashboard.

3. Calibration Workflow

• Tank Sensor Calibration (Input) Figure 1: When your physical fuel tank is at Empty, Mid (50%), and Full levels, click the corresponding Set button on the web dashboard to capture the real-time Sensor value. Or manually input value and click Save Tank Config to apply.
• Gauge Calibration (Output) Figure 2: On the web dashboard, manually adjust the Min PWM, Mid PWM, and Max PWM values while watching your physical gauge. Tweak the numbers until the needle points perfectly to E, 1/2, and F marks, then click Save Gauge Config. Check Technical Reference for Gauge Output mapping.

  Figure 1                                                               Figure 2

Part 2: Technical Reference

1. Hardware Pin Configuration

The hardware input/output mapping is defined as follows:

• Sensor Inputs:

• Tank 1: GPIO 6
• Tank 2: GPIO 0
• Tank 3: GPIO 1
• Tank 4: GPIO 2

• Gauge Outputs:

• Gauge 1 (Mapped to Tank 1): GPIO 16
• Gauge 2 (Mapped to Gauge3 Tank 2): GPIO 21
• Gauge 3 (Mapped to Gauge3 Tank 3): GPIO 22
• Gauge 4 (Mapped to Gauge3 Tank 4): GPIO 23
• Gauge 5 (Mapped to Gauge2 Tank 2 or 3): GPIO 18

• Gauge 5 Output Control Pins (Internal Pull-Up enabled):

• Select Tank 2: GPIO 20 (Active LOW)
• Select Tank 3: GPIO 19 (Active LOW)

2. HTTP API Protocol

The built-in Web Server provides RESTful HTTP GET endpoints for front-end interaction:

3. JSON Payload Memory Map

When the front-end calls the /status endpoint, the system returns a JSON payload structured as follows:

JSON

{
 "tanks": [
   {"adc": 2048, "e": 20, "m": 2000, "f": 4000},
   {"adc": 1500, "e": 50, "m": 1800, "f": 3800},
   {"adc": 0, "e": 20, "m": 2000, "f": 4000},
   {"adc": 0, "e": 20, "m": 2000, "f": 4000}
 ],
 "gauges": [
   {"pwm": 200, "min": 40, "mid": 200, "max": 410},
   {"pwm": 150, "min": 50, "mid": 210, "max": 420},
   {"pwm": 40, "min": 40, "mid": 200, "max": 410},
   {"pwm": 40, "min": 40, "mid": 200, "max": 410},
   {"pwm": 0, "min": 40, "mid": 200, "max": 410}
 ]
}

Parsing Guide:

• The tanks array contains 4 objects corresponding to Tanks 1-4. adc is the current real-time sensor reading (after a 15-sample smoothing filter). e, m, and f are the saved Empty, Mid, and Full calibration thresholds.
• The gauges array contains 5 objects corresponding to Gauges 1-5. pwm is the real-time duty cycle currently being output. min, mid, and max are the saved gauge calibration boundaries.

4. Mapping Algorithm

The system eschews simple linear mapping in favor of a Midpoint-based piecewise linear interpolation. The algorithm automatically detects whether the sensor utilizes forward resistance (Empty -> Full = resistance increases) or inverted resistance (Empty -> Full = resistance decreases):

• If the real-time adc ≤ Mid, the system uses linear interpolation based on the slope between Empty and Mid.
• If the real-time adc > Mid, the system uses linear interpolation based on the slope between Mid and Full.
• Safety Clamp: If the calculated output exceeds the calibrated extreme boundaries, the system enforces a hard clamp at the software level to prevent hardware coil damage.