Four-Wheel RC Car Wiring

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1. 01

   Prepare the power wiring

   With the LiPo disconnected, wire battery +V (red, marked +) to the IN terminal of power_switch. Wire power_switch OUT as the switched-LiPo-positive junction. From this same OUT junction, run one wire to l9110s_1 VCC and one wire to buckboost_3v3 VIN. Wire lipo_1s GND (black, marked −), buckboost_3v3 GND, l9110s_1 GND, and the ESP32 GND pin into one common-ground junction.

   • Tip: Use heavier, short wire for the battery, switch, driver VCC, and ground paths because motor current flows there.
   • Tip: A star-like common-ground junction near the L9110S/battery return helps reduce motor noise.

   • ⚠ Observe LiPo polarity. A reversed LiPo can destroy the converter and driver.
   • ⚠ Do not connect the raw LiPo positive lead directly to the LOLIN S2 Mini 3V3 pin.
   • ⚠ This parts list has no charging circuit: charge the protected LiPo only with a proper single-cell LiPo charger, disconnected from the car if the charger requires it.
2. 02

   Set and connect the 3.3 V converter

   Before connecting the ESP32, power the switched input from the LiPo and use a multimeter to set buckboost_3v3 VOUT to exactly 3.3 V. Switch power off, then connect VOUT to the LOLIN S2 Mini 3V3 pin and leave its GND connected to the common-ground junction from step 1. Fit esp_decoupling_cap directly between the ESP32 3V3 and GND pins.

   • Tip: Keep the 100 nF ceramic capacitor leads very short.
   • Tip: If the chosen converter has an EN pin that must be driven high, follow its module markings; many modules already tie EN high.

   • ⚠ Check 3.3 V with a meter before the ESP32 is attached. Never feed more than 3.3 V into its 3V3 pin.
3. 03

   Add driver supply filtering and logic wiring

   Fit motor_bulk_cap close to l9110s_1: capacitor + to L9110S VCC and capacitor − to common ground. Observe its stripe-marked negative lead. Connect LOLIN S2 Mini GPIO9 to L9110S A-IA, GPIO10 to A-IB, GPIO11 to B-IA, and GPIO12 to B-IB. The driver and ESP32 grounds must remain common.

   • Tip: Keep the four GPIO control wires away from motor wires where possible.
   • Tip: The 470 µF electrolytic should be rated at least 6.3 V; 10 V or higher is also suitable.

   • ⚠ The 470 µF capacitor is polarized: its negative-striped lead goes only to GND.
   • ⚠ Do not use GPIO9–GPIO12 for another function in this build.
4. 04

   Wire channel A to both left motors

   Make a parallel pair from L9110S channel A: connect A-OUT1 to left_front_motor M+ and left_rear_motor M+. Connect A-OUT2 to left_front_motor M− and left_rear_motor M−. Solder lf_motor_cap directly across the left-front motor terminals and lr_motor_cap directly across the left-rear motor terminals.

   • Tip: The two branch junctions at A-OUT1 and A-OUT2 are the required parallel connection for the left side.
   • Tip: Place each 100 nF capacitor physically on its motor terminals, not back at the driver.

   • ⚠ The combined stall current of the left-front and left-rear motors must remain within the L9110S channel-current rating. Do not estimate from running current alone; use stall-current data or measure it.
5. 05

   Wire channel B to both right motors

   Make a parallel pair from L9110S channel B: connect B-OUT1 to right_front_motor M+ and right_rear_motor M+. Connect B-OUT2 to right_front_motor M− and right_rear_motor M−. Solder rf_motor_cap across the right-front motor terminals and rr_motor_cap across the right-rear motor terminals.

   • Tip: Keep left and right motor-pair wiring similar in length and thickness.
   • Tip: Secure motor leads so vibration cannot fatigue the solder joints.

   • ⚠ The combined stall current of the right-front and right-rear motors must remain within the L9110S channel-current rating. If either pair overloads the driver, use lower-current motors or a higher-current driver.
6. 06

   Check rotation and operate the car

   Raise the car so all wheels are clear, turn on power, and use Schematik’s Deploy button to flash the firmware. On a phone, join Wi‑Fi network S2-RC-Car using password drivecar, then open http://192.168.4.1. Press Forward briefly. If one wheel turns opposite to the other wheel on the same side, switch off power and reverse only that motor’s two wires; keep its 100 nF capacitor across its two terminals.

   • Tip: Test while the wheels are off the bench first.
   • Tip: If forward/reverse is swapped for all four wheels, swap the forward/reverse logic in firmware rather than rewiring every motor.

   • ⚠ Keep fingers, loose wires, and clothing clear of spinning wheels.
   • ⚠ Stop immediately if the L9110S becomes very hot, the battery protection trips, or the ESP32 resets when accelerating.

#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>

#define LEFT_IA_PIN 9
#define LEFT_IB_PIN 10
#define RIGHT_IA_PIN 11
#define RIGHT_IB_PIN 12


// Forward declarations
void stopCar();
void setLeft(bool forward);
void setRight(bool forward);
void handleCommand();
void handleRoot();

const char *AP_SSID = "S2-RC-Car";
const char *AP_PASSWORD = "drivecar";

WebServer server(80);

void stopCar() {
  digitalWrite(LEFT_IA_PIN, LOW);
  digitalWrite(LEFT_IB_PIN, LOW);
  digitalWrite(RIGHT_IA_PIN, LOW);
  digitalWrite(RIGHT_IB_PIN, LOW);
}

void setLeft(bool forward) {
  digitalWrite(LEFT_IA_PIN, forward ? HIGH : LOW);
  digitalWrite(LEFT_IB_PIN, forward ? LOW : HIGH);
}

void setRight(bool forward) {
  digitalWrite(RIGHT_IA_PIN, forward ? HIGH : LOW);
  digitalWrite(RIGHT_IB_PIN, forward ? LOW : HIGH);
}

void handleCommand() {
  String command = server.arg("c");

  if (command == "forward") {
    setLeft(true);
    setRight(true);
  } else if (command == "back") {
    setLeft(false);
    setRight(false);
  } else if (command == "left") {
    setLeft(false);
    setRight(true);
  } else if (command == "right") {
    setLeft(true);
    setRight(false);
  } else {
    stopCar();
  }

  server.send(200, "text/plain", "OK");
}

void handleRoot() {
  const char page[] = R"rawliteral(
<!doctype html><html><head><meta name="viewport" content="width=device-width,initial-scale=1">
<style>body{font-family:sans-serif;text-align:center;background:#151515;color:#fff;margin:0;padding:24px}button{width:120px;height:68px;margin:7px;font-size:20px;border:0;border-radius:10px;background:#2574d9;color:#fff}button.stop{background:#c93636}</style>
</head><body><h2>ESP32-S2 RC Car</h2><p>Hold a direction button to drive; releasing it stops the car.</p>
<div><button data-c="forward">Forward</button></div><div><button data-c="left">Left</button><button data-c="right">Right</button></div><div><button data-c="back">Reverse</button></div><div><button class="stop" data-c="stop">STOP</button></div>
<script>document.querySelectorAll('button').forEach(b=>{const go=()=>fetch('/cmd?c='+b.dataset.c);b.onpointerdown=go;b.onpointerup=()=>fetch('/cmd?c=stop');b.onpointerleave=()=>fetch('/cmd?c=stop');b.onpointercancel=()=>fetch('/cmd?c=stop');});</script>
</body></html>
)rawliteral";
  server.send(200, "text/html", page);
}

void setup() {
  pinMode(LEFT_IA_PIN, OUTPUT);
  pinMode(LEFT_IB_PIN, OUTPUT);
  pinMode(RIGHT_IA_PIN, OUTPUT);
  pinMode(RIGHT_IB_PIN, OUTPUT);
  stopCar();

  WiFi.mode(WIFI_AP);
  WiFi.softAP(AP_SSID, AP_PASSWORD);

  server.on("/", HTTP_GET, handleRoot);
  server.on("/cmd", HTTP_GET, handleCommand);
  server.begin();
}

void loop() {
  server.handleClient();
}

“Deploy to device” opens this project in Schematik, where you can flash it to your board over USB.