ESP32 ALDL Dashboard

An Android application built using Jetpack Compose to display real-time engine telemetry from a 1986 Pontiac Fiero 2.8L V6 (1227170 ECM). The app connects to a Bluetooth serial device named ESP32-ALDL and decodes a raw binary stream of 27-byte frames containing ECM data packets under the $24 mask specifications.

Technical Specifications

Data Stream Frame Structure

The ESP32 reads the raw 160-baud unidirectional ALDL stream from the ECM and encapsulates it in a 27-byte packet transmitted over Bluetooth SPP.

Byte Index	Length	Value / Field	Description
0 - 1	2 bytes	`AA 55`	Frame Sync Header (added by ESP32)
2 - 26	25 bytes	Raw Data Payload	1227170 ECM data stream (0-indexed indices 0 to 24)

Parameter Offsets & Decoding Formulas

The telemetry parameters are parsed from the $24 / $24A ECM mask definitions (24-INT10.ads). In TunerPro's .ads file, the byte numbers are 1-indexed (e.g. btByteNumber = 4 maps to raw payload byte index 3).

1. Primary Sensors & Measurements

Parameter	Payload Index	Raw Size	Formula / Conversion	Units
IAC Position	Index 3 (Byte 4)	8-bit	`Value = Raw`	Steps
Coolant Temp	Index 4 (Byte 5)	8-bit	$C = (Raw \times 0.75) - 40$ `F = (Raw \times 1.35) - 40`	°C / °F
Vehicle Speed	Index 5 (Byte 6)	8-bit	`Value = Raw` (Operation 3)	MPH
MAP	Index 6 (Byte 7)	8-bit	$Volts = Raw \times 0.019608$ `kPa = (Raw \times 0.369) + 10.354`	Volts / kPa
Engine Speed	Index 7 (Byte 8)	8-bit	`RPM = Raw \times 25`	RPM
TPS	Index 8 (Byte 9)	8-bit	`Volts = Raw \times 0.019608`	Volts
Integrator (INT)	Index 9 (Byte 10)	8-bit	`Value = Raw`	—
O2 Sensor	Index 10 (Byte 11)	8-bit	`mV = Raw \times 4.44`	mV
Battery Voltage	Index 17 (Byte 18)	8-bit	`Volts = Raw \times 0.1`	Volts
BLM	Index 18 (Byte 19)	8-bit	`Value = Raw`	—
Rich/Lean Crosses	Index 19 (Byte 20)	8-bit	`Value = Raw`	Crosses
Spark Advance	Index 20 (Byte 21)	8-bit	`Degrees = Raw \times 0.351563`	Degrees
EGR Duty Cycle	Index 21 (Byte 22)	8-bit	`Percent = Raw \times 0.392157`	%
Manifold Air Temp (MAT)	Index 22 (Byte 23)	8-bit	Linear Table Interpolation (see below)	°C / °F
Base Pulse Width (BPW)	Index 23-24 (Byte 24-25)	16-bit	$Raw = (HighByte \ll 8) \vert LowByte$ `ms = Raw \times 0.015259`	Milliseconds (ms)

2. MAT Linear Interpolation Tables

The Manifold Air Temperature (MAT) is read from Index 22. It is mapped to degrees C or F using interpolation curves specified in tables 52 and 53:

Celsius (MAT C - Table 52):
- 0 -> 200.0, 12 -> 150.0, 13 -> 145.0, 14 -> 140.0, 16 -> 135.0, 18 -> 130.0, 21 -> 125.0, 23 -> 120.0, 26 -> 115.0, 30 -> 110.0, 34 -> 105.0, 39 -> 100.0, 44 -> 95.0, 50 -> 90.0, 56 -> 85.0, 64 -> 80.0, 72 -> 75.0, 81 -> 70.0, 92 -> 65.0, 102 -> 60.0, 114 -> 55.0, 126 -> 50.0, 139 -> 45.0, 152 -> 40.0, 165 -> 35.0, 177 -> 30.0, 189 -> 25.0, 199 -> 20.0, 209 -> 15.0, 218 -> 10.0, 225 -> 5.0, 231 -> 0.0, 237 -> -5.0, 241 -> -10.0, 245 -> -15.0, 247 -> -20.0, 250 -> -25.0, 251 -> -30.0, 255 -> -40.0
Fahrenheit (MAT F - Table 53):
- 0 -> 392.0, 12 -> 302.0, 13 -> 293.0, 14 -> 284.0, 16 -> 275.0, 18 -> 266.0, 21 -> 257.0, 23 -> 248.0, 26 -> 239.0, 30 -> 230.0, 34 -> 221.0, 39 -> 212.0, 44 -> 203.0, 50 -> 194.0, 56 -> 185.0, 64 -> 176.0, 72 -> 167.0, 81 -> 158.0, 92 -> 149.0, 102 -> 140.0, 114 -> 131.0, 126 -> 122.0, 139 -> 113.0, 152 -> 104.0, 165 -> 95.0, 177 -> 86.0, 189 -> 77.0, 199 -> 68.0, 209 -> 59.0, 218 -> 50.0, 225 -> 41.0, 231 -> 32.0, 237 -> 23.0, 241 -> 14.0, 245 -> 5.0, 247 -> -4.0, 250 -> -13.0, 251 -> -22.0, 255 -> -40.0

3. Stored Fault Trouble Codes

Malfunction Indicator Codes are mapped as bit flags across three specific status bytes:

Codes Byte 1 (Payload Index 11 / Byte 12)

Bit 7: Code 12 - Crank Sensor / System Check
Bit 6: Code 13 - O2 Sensor
Bit 5: Code 14 - Coolant High Temp
Bit 4: Code 15 - Coolant Low Temp
Bit 3: Code 21 - TPS Voltage High
Bit 2: Code 22 - TPS Voltage Low
Bit 1: Code 23 - MAT Voltage Low
Bit 0: Code 24 - Vehicle Speed Sensor (VSS)

Codes Byte 2 (Payload Index 12 / Byte 13)

Bit 7: Code 25 - MAT Voltage High
Bit 5: Code 32 - EGR System
Bit 4: Code 33 - MAP Sensor High
Bit 3: Code 34 - MAP Sensor Low
Bit 2: Code 35 - IAC Position
Bit 0: Code 42 - Electronic Spark Timing (EST)

Codes Byte 3 (Payload Index 13 / Byte 14)

Bit 7: Code 43 - Electronic Spark Control (Knock Sensor)
Bit 6: Code 44 - O2 Sensor Lean Exhaust
Bit 5: Code 45 - O2 Sensor Rich Exhaust
Bit 4: Code 51 - PROM Error
Bit 3: Code 52 - Cal-Pack Error
Bit 2: Code 53 - System Battery Over-Voltage
Bit 0: Code 55 - ADU Error

4. Engine Status & Bit Flags

Misc Byte 1 (Payload Index 14 / Byte 15)

Bit 1: BLM Enabled (1 = Yes)
Bit 3: Quasi Pulse Mode (1 = Yes)
Bit 4: Async Pulse Mode (1 = Yes)
Bit 6: Rich/Lean Status (1 = Rich, 0 = Lean)
Bit 7: Loop Status (1 = Closed, 0 = Open)

Misc Byte 2 (Payload Index 15 / Byte 16)

Bit 5: A/C Status (0 = Enabled, 1 = Disabled/Idle)
Bit 7: Park/Neutral Switch (1 = Park/Neutral, 0 = In Gear)

Misc Byte 3 (Payload Index 16 / Byte 17)

Bit 0: A/C Clutch Command (1 = Enabled)
Bit 2: Torque Converter Clutch (TCC) (1 = Locked)
Bit 5: Power Steering Cramp Switch (1 = Active)

App Features & Architecture

Bluetooth Thread Management:
- Queries for paired devices and connects directly to "ESP32-ALDL" over standard SPP RFCOMM sockets.
- Robust frame synchronization: buffers incoming streams and aligns on the double-byte header 0xAA 0x55.
State Management:
- State flows from the Bluetooth thread through Kotlin StateFlow to Compose UI.
Modern Dash Dashboard UI:
- Dynamic animations for RPM and TPS sweeps.
- Metrics displayed in responsive tiles with custom indicator colors (e.g. engine loop states, fuel trims, battery health).
- Live trouble code alert panel.
- Diagnostic pane displaying real-time raw hex buffers for physical signal verification.

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