Airspeed PCB

Custom PCB system for capturing real-time air pressure data across aerodynamic components on a Formula SAE race car.

AltiumC++React.js

The Board

A standalone data acquisition board designed for aerodynamic testing on a Formula SAE race car. During testing, 12 Honeywell differential pressure sensors connect to pitot tubes mounted on an aero-rig. The sensors measure differential pressure across aerodynamic surfaces, providing the aero team with real-world data to validate their CFD models. Data is logged through the ESP32's flash memory and stored long-term as .csv files on an SD card for post-session analysis.

Component	Role
ESP32-S3-DevKitC-1	Main microcontroller with built-in WiFi and USB CDC
Honeywell ABP2 Sensors (×12)	Differential pressure measurement via pitot tubes
TCA9548A I2C Mux (×2)	Route 12 sensors on a shared I2C bus
PCF8523 RTC	Real-time clock for timestamping logged data
CAN Transceiver	Vehicle CAN bus integration

The Code

FILES

▫main.cpp

1#include <Arduino.h>
2#include <Wire.h>
3#include <virtualTimer.h>
4#include "TCA9548A.h"
5#include "airSpeed.h"
6#include "PCF8523.h"
7 
8// GPIO Definitions
9#define SDA_PIN 21
10#define SCL_PIN 22
11 
12// SD card pins
13#define SD_MISO 27
14#define SD_CLK  14
15#define SD_MOSI 13
16#define SD_CS   15
17 
18// Hardware stuff
19TCA9548A muxA(0x70);          // MUX A at address 0x70
20TCA9548A muxB(0x71);          // MUX B at address 0x71
21PCF8523_RTC rtc;
22 
23// Airspeed sensors
24// MUX A channels 0-7, MUX B channels 0-3
25static constexpr uint8_t MUX_A_COUNT = 6;
26static constexpr uint8_t MUX_B_COUNT = 6;
27static constexpr uint8_t SENSOR_COUNT = MUX_A_COUNT + MUX_B_COUNT;
28 
29AirSpeedSensor sensorsA[] = {
30    AirSpeedSensor(muxA, 0), AirSpeedSensor(muxA, 1),
31    AirSpeedSensor(muxA, 2), AirSpeedSensor(muxA, 3),
32    AirSpeedSensor(muxA, 4), AirSpeedSensor(muxA, 5),
33};
34 
35AirSpeedSensor sensorsB[] = {
36    AirSpeedSensor(muxB, 0), AirSpeedSensor(muxB, 1),
37    AirSpeedSensor(muxB, 2), AirSpeedSensor(muxB, 3),
38    AirSpeedSensor(muxB, 4), AirSpeedSensor(muxB, 5),
39};
40 
41// Readings storage
42ABP2Reading readings[SENSOR_COUNT];
43RTCTime currentTime;
44 
45// Timer group
46VirtualTimerGroup timerGroup;
47 
48// Forward declarations
49void pollSensors();
50void printData();
51 
52// Callbacks
53void pollSensors() {
54    // Read RTC
55    currentTime = rtc.readTime();
56 
57    // Read all MUX A sensors
58    for (uint8_t i = 0; i < MUX_A_COUNT; i++) {
59        readings[i] = sensorsA[i].read();
60    }
61 
62    // Read all MUX B sensors
63    for (uint8_t i = 0; i < MUX_B_COUNT; i++) {
64        readings[MUX_A_COUNT + i] = sensorsB[i].read();
65    }
66}
67 
68void printData() {
69    // Print RTC timestamp
70    if (currentTime.valid) {
71        char ts[24];
72        snprintf(ts, sizeof(ts), "20%02u-%02u-%02u %02u:%02u:%02u",
73                 currentTime.year, currentTime.month, currentTime.day,
74                 currentTime.hours, currentTime.minutes, currentTime.seconds);
75        Serial.print("[");
76        Serial.print(ts);
77        Serial.print("] ");
78        if (currentTime.os_flag) Serial.print("(RTC CLOCK LOST) ");
79    } else {
80        Serial.print("[RTC ERROR] ");
81    }
82 
83    Serial.print("t=");
84    Serial.print(millis());
85    Serial.println("ms");
86 
87    // Print each sensor reading
88    for (uint8_t i = 0; i < SENSOR_COUNT; i++) {
89        const char *muxLabel = (i < MUX_A_COUNT) ? "A" : "B";
90        uint8_t ch = (i < MUX_A_COUNT) ? i : (i - MUX_A_COUNT);
91 
92        Serial.print("  MUX");
93        Serial.print(muxLabel);
94        Serial.print(":CH");
95        Serial.print(ch);
96 
97        if (readings[i].valid) {
98            Serial.print("  P=");
99            Serial.print(readings[i].pressure_inH2O, 4);
100            Serial.print(" inH2O  T=");
101            Serial.print(readings[i].temperature_C, 1);
102            Serial.println(" C");
103        } else {
104            Serial.print("  INVALID (status=0x"); // error catching
105            Serial.print(readings[i].status, HEX);
106            Serial.println(")");
107        }
108    }
109    Serial.println("---");
110}
111 
112void setup() {
113    Serial.begin(9600);
114    Wire.begin(SDA_PIN, SCL_PIN);
115 
116    Serial.println("DAQ Airspeed — Initializing...");
117 
118    // Init MUXes
119    if (!muxA.begin()) Serial.println("ERROR: MUX A (0x70) not found!");
120    if (!muxB.begin()) Serial.println("ERROR: MUX B (0x71) not found!");
121 
122    // Init RTC
123    if (!rtc.begin()) {
124        Serial.println("ERROR: PCF8523 RTC not found!");
125    } else {
126        Serial.println("PCF8523 RTC OK");
127    }
128 
129    // Init sensors — report which ones respond
130    Serial.print("Sensors on MUX A: ");
131    for (uint8_t i = 0; i < MUX_A_COUNT; i++) {
132        bool ok = sensorsA[i].begin();
133        Serial.print(ok ? "+" : "-");
134    }
135    Serial.println();
136 
137    Serial.print("Sensors on MUX B: ");
138    for (uint8_t i = 0; i < MUX_B_COUNT; i++) {
139        bool ok = sensorsB[i].begin();
140        Serial.print(ok ? "+" : "-");
141    }
142    Serial.println();
143 
144    // CSV-style header for serial
145    Serial.println();
146    Serial.println("timestamp, millis, mux, ch, inH2O, temp_C");
147    Serial.println("========================================================");
148 
149    // Schedule repeating timers
150    timerGroup.AddTimer(1000, pollSensors);   // poll sensors every 1s
151    timerGroup.AddTimer(1000, printData);     // print to serial every 1s
152 
153    Serial.println("Timers started.");
154}
155 
156void loop() {
157    timerGroup.Tick(millis());
158}

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