Dual GNSS RTK Controller Board, a ESP32 project

This dual GNSS RTK controller board brings centimeter-level positioning to robotics and autonomous systems by managing two independent Quectel LC29H RTK modules on a single ESP32-S3 platform. The board accepts 24 V input, distributes regulated 3.3 V power across multiple branches, and routes dual GNSS antenna signals through SMA connectors while handling serial communication via level-translated UART interfaces.

Builders will receive a complete wiring diagram, detailed parts list, assembly sequence with inspection checkpoints, and Arduino firmware that initializes both GPS receivers at 115200 baud, manages CAN bus communication, and logs data to microSD card. The guide covers power distribution, antenna routing, UART translation, and motor control signal integration, with step-by-step instructions designed to ensure reliable RTK performance before applying main power.

Wiring diagram

Gather all the parts

Qty	Component
1	24 V locking power-input terminal 2-position, ≥30 V A two-position screw terminal that brings the external 24 V supply safely onto the PCB.
1	24v Buck Converter 5 V, ≥1 A LM2596-based adjustable step-down buck converter module. Commonly used to regulate a higher battery rail, such as a 2S 18650 pack, down to 5V for Arduino logic. It is a regulator, not a charger or battery protection board.
1	AMS1117 3.3V Regulator 3.3 V Linear LDO regulator, 5 V (or higher) in -> 3.3 V out, 1 A max. Used to drop a 5 V supply down to 3.3 V for ESP32 / Pico when no on-board regulator is available.
1	AMS1117 3.3V Regulator 3.3 V Linear LDO regulator, 5 V (or higher) in -> 3.3 V out, 1 A max. Used to drop a 5 V supply down to 3.3 V for ESP32 / Pico when no on-board regulator is available.
1	Quectel LC29H GNSS RTK module 1 LC29H The first high-precision satellite receiver, used to provide position and RTK correction data.
1	Quectel LC29H GNSS RTK module 2 LC29H The second high-precision satellite receiver, used independently from the first receiver.
1	GPS 1 dual-channel directional UART level translator SN74LVC2T45 A directional logic translator that safely converts the first GPS module’s 2.8 V UART signals to ESP32 3.3 V signals.
1	GPS 2 dual-channel directional UART level translator SN74LVC2T45 A directional logic translator that safely converts the second GPS module’s 2.8 V UART signals to ESP32 3.3 V signals.
1	Motor-controller signal connector 3-position A three-position locking connector carrying two 3.3 V command signals and ground to the motor controller.
1	Secondary ESP32 UART connector 3-position A three-position connector for 3.3 V serial data and ground to another ESP32.
1	GPS 1 SMA GNSS antenna connector SMA, 50 Ω A 50-ohm coaxial connector for the first external GNSS antenna.
1	GPS 2 SMA GNSS antenna connector SMA, 50 Ω A 50-ohm coaxial connector for the second external GNSS antenna.
1	ESP32-S3 3.3 V regulator TLV75533P, 3.3 V / 500 mA A regulator that turns the protected 5 V rail into the stable 3.3 V supply required by the ESP32-S3 and UART translator high-voltage sides.
1	Adafruit CAN Pal - CAN Bus Transceiver 3.3 V CAN transceiver CAN bus transceiver breakout that converts 3 V CAN peripheral signals (TX/RX) to differential CAN bus levels. Compatible with ESP32/S2/S3 (TWAI), SAME51, STM32F405, and Teensy 4; not all MCUs have a CAN peripheral.
1	Resistor 120 Ω, DNP option Through-hole resistor (current-limiting in series with an LED)
1	CAN bus connector 3-position CAN terminal A three-position connector carrying CANH, CANL, and ground to the other ESP32.
1	Adafruit MicroSD SPI/SDIO Breakout Board (3V Only) 3.3 V SPI microSD socket MicroSD card breakout for adding file storage to a microcontroller project, wired over SPI (any MCU) or native SDIO (faster, needs SDIO hardware/firmware support like SAMD51). Board has no onboard regulator or level shifter, so it runs on 3.3V logic and power only — do not connect directly to a 5V system.

Assemble it in 8 steps

1. Place the power-input parts

Fit power_input_24v, buck_24v_to_5v, and controller_3v3_regulator at the board edge. Keep the 24 V input tracks wide and short, and place the buck converter’s input and output capacitors immediately beside its pins so supply spikes stay away from the rest of the board.

Mark the terminal clearly: +24V and GND.
Use a locking two-position terminal rated above 24 V.
Do not connect 24 V to any 5 V or 3.3 V net — that can immediately damage the ESP32 and GPS modules.

2. Build the three 3.3 V supply branches

Fit gps1_ldo and gps2_ldo with the capacitors required by their regulator datasheets. Route each regulator output only to its own LC29H module first, then connect all grounds to one solid ground plane. This gives each receiver its own cleaner supply branch even though they share the 24 V input.

Place each GPS regulator and its capacitors close to the module it powers.
Keep the switching buck converter and its inductor as far as practical from both GPS modules and antenna connectors.
Make sure VCC and GND are not swapped on either GPS module — swapped power can damage the receiver.

3. Route both GPS antenna paths

Place gps1_antenna_connector and gps2_antenna_connector at a board edge. Route each connector directly to its matching LC29H RF_IN pin as a controlled 50-ohm track, with no branches and a continuous ground reference underneath. Keep the two RF tracks apart and away from the buck converter, motor connector, and fast digital tracks.

Follow the LC29H reference layout for the RF matching network and antenna keep-out area.
Use active GNSS antennas only if the selected LC29H antenna circuit includes the required bias feed and protection parts.
Do not run a GPS RF track under or beside the buck converter inductor — electrical noise can prevent accurate position fixes.

4. Wire the GPS serial translators

Fit gps1_uart_level_shifter and gps2_uart_level_shifter between the ESP32-S3 and the GPS modules. Connect GPS 1 through GPIO5 and GPIO4, and GPS 2 through GPIO7 and GPIO6. The translator’s low-voltage side uses each LC29H VDD_EXT reference, while its other side uses the ESP32 3.3 V rail; this prevents 3.3 V logic from being forced into the GPS module’s 2.8 V serial pins.

Keep each UART pair short and route each pair together.
Check the translator direction pins against the schematic before ordering the PCB: GPS TX must reach ESP32 RX, and ESP32 TX must reach GPS RX.
Do not bypass the level translators — a direct 3.3 V ESP32 output can overstress the LC29H’s 2.8 V serial input.

5. Fit the UART comparison connector

Fit esp32_serial_connector as a three-position connector: TX to GPIO15 (data), RX to GPIO16 (data), and GND to the ground plane (ground). At the second ESP32, cross the two data wires: this board’s TX goes to its RX, and this board’s RX goes to its TX.

Keep this cable short and away from motor wires.
Label TX, RX, and GND on both boards.
Only connect it to 3.3 V UART pins — a 5 V serial signal can damage the ESP32.

6. Fit the CAN comparison connector

Fit can_transceiver and can_connector. Connect GPIO21 to the transceiver TX input (data), GPIO14 to its RX output (data), VCC to 3V3 (power), and GND to GND (ground). Connect CANH and CANL from the transceiver to the matching CANH and CANL terminals on can_connector; connect the connector GND to GND (ground). Fit can_termination_resistor across CANH and CANL only when this board is at one physical end of the CAN cable.

Use a twisted pair for CANH and CANL.
Use the same CAN speed, 500 kbit/s, on the other ESP32 during the comparison.
Do not connect CANH or CANL directly to an ESP32 GPIO — the transceiver is the protective translator between the chip and the cable.
Install exactly two 120-ohm termination resistors in the whole CAN cable, one at each physical end; extra resistors make the signal weaker.

7. Fit the microSD card socket

Fit microsd_storage near the ESP32-S3, but away from the GPS antenna area and the buck converter. Connect 3V to 3V3 (power), GND to GND (ground), CLK to GPIO12 (clock), MISO to GPIO13 (data from card), MOSI to GPIO11 (data to card), and CS to GPIO10 (card select). Insert a FAT32-formatted microSD card only after the board has been checked for correct 3.3 V power.

Keep CLK, MISO, MOSI, and CS short and route them over an unbroken ground plane.
Use a 3.3 V-only socket or breakout; the selected design has no 5 V protection.
Never connect the microSD 3V pin to the 5 V rail — 5 V can damage the card and its socket electronics.
Do not insert or remove the card while the board is powered unless the final firmware explicitly supports safe removal.

8. Fit the motor connector and inspect before applying 24 V

Fit motor_controller_connector as a three-position connector: SIG1 to GPIO17 (signal), SIG2 to GPIO18 (signal), and GND to the ground plane (ground). Before connecting 24 V, use a multimeter to check that +24V is not shorted to GND, then check that the buck output is 5 V and the three regulator outputs are 3.3 V. Only then install the ESP32-S3 and GPS modules, attach antennas, insert the microSD card, and connect external cables.

The firmware holds both motor signals low whenever the ESP32 starts.
Power up without the GPS modules installed first if you can; it makes a wiring mistake easier to find.
Only connect the motor-controller connector to a controller confirmed to accept 3.3 V logic — a higher-voltage signal on GPIO17 or GPIO18 can damage the ESP32.
Never probe or move connector wiring while the 24 V supply is connected — a slipped probe can short the supply and damage PCB tracks.

Review all connections

1. Connections between "power_input_24v" and "ESP32"

Function	power_input_24v	ESP32
`power`	+24V → 24v Buck Converter VIN+	EXT
`ground`	GND	GND

2. Connections between "buck_24v_to_5v" and "ESP32"

Function	buck_24v_to_5v	ESP32
`ground`	VIN-	GND
`power`	VOUT+	5V
`ground`	VOUT-	GND

3. Connections between "gps1_ldo" and "ESP32"

Function	gps1_ldo	ESP32
`power`	VIN	5V
`power`	VOUT → Quectel LC29H GNSS RTK module 1 VCC	EXT
`ground`	GND	GND

4. Connections between "gps2_ldo" and "ESP32"

Function	gps2_ldo	ESP32
`power`	VIN	5V
`power`	VOUT → Quectel LC29H GNSS RTK module 2 VCC	EXT
`ground`	GND	GND

5. Connections between "lc29h_1" and "ESP32"

Function	lc29h_1	ESP32
`power`	V_BCKP → AMS1117 3.3V Regulator VOUT	EXT
`ground`	GND	GND
`uart`	TXD1 → GPS 1 dual-channel directional UART level translator A1	EXT
`uart`	RXD1 → GPS 1 dual-channel directional UART level translator A2	EXT
`power`	VDD_EXT → GPS 1 dual-channel directional UART level translator VCCA	EXT

6. Connections between "lc29h_2" and "ESP32"

Function	lc29h_2	ESP32
`power`	V_BCKP → AMS1117 3.3V Regulator VOUT	EXT
`ground`	GND	GND
`uart`	TXD1 → GPS 2 dual-channel directional UART level translator A1	EXT
`uart`	RXD1 → GPS 2 dual-channel directional UART level translator A2	EXT
`power`	VDD_EXT → GPS 2 dual-channel directional UART level translator VCCA	EXT

7. Connections between "gps1_uart_level_shifter" and "ESP32"

Function	gps1_uart_level_shifter	ESP32
`power`	VCCB	3V3
`ground`	GND	GND
`uart`	B1	GPIO 5
`power`	DIR1	3V3
`uart`	B2	GPIO 4
`ground`	DIR2	GND

8. Connections between "gps2_uart_level_shifter" and "ESP32"

Function	gps2_uart_level_shifter	ESP32
`power`	VCCB	3V3
`ground`	GND	GND
`uart`	B1	GPIO 7
`power`	DIR1	3V3
`uart`	B2	GPIO 6
`ground`	DIR2	GND

9. Connections between "gps1_antenna_connector" and "ESP32"

Function	gps1_antenna_connector	ESP32
`data`	RF → Quectel LC29H GNSS RTK module 1 RF_IN	EXT
`ground`	GND	GND

10. Connections between "gps2_antenna_connector" and "ESP32"

Function	gps2_antenna_connector	ESP32
`data`	RF → Quectel LC29H GNSS RTK module 2 RF_IN	EXT
`ground`	GND	GND

11. Connections between "motor_controller_connector" and "ESP32"

Function	motor_controller_connector	ESP32
`digital`	SIG1	GPIO 17
`digital`	SIG2	GPIO 18
`ground`	GND	GND

12. Connections between "esp32_serial_connector" and "ESP32"

Function	esp32_serial_connector	ESP32
`uart`	TX	GPIO 15
`uart`	RX	GPIO 16
`ground`	GND	GND

13. Connections between "controller_3v3_regulator" and "ESP32"

Function	controller_3v3_regulator	ESP32
`power`	VIN	5V
`power`	VOUT	3V3
`ground`	GND	GND

14. Connections between "can_transceiver" and "ESP32"

Function	can_transceiver	ESP32
`power`	VCC	3V3
`ground`	GND	GND
`data`	TX	GPIO 21
`data`	RX	GPIO 14
`data`	CANH → CAN bus connector CANH	EXT
`data`	CANL → CAN bus connector CANL	EXT

15. Connections between "can_termination_resistor" and "ESP32"

Function	can_termination_resistor	ESP32
`digital`	P1 → Adafruit CAN Pal - CAN Bus Transceiver CANH	EXT
`digital`	P2 → Adafruit CAN Pal - CAN Bus Transceiver CANL	EXT

16. Connections between "can_connector" and "ESP32"

Function	can_connector	ESP32
`ground`	GND	GND

17. Connections between "microsd_storage" and "ESP32"

Function	microsd_storage	ESP32
`power`	3V	3V3
`ground`	GND	GND
`spi`	CLK	GPIO 12
`spi`	MISO	GPIO 13
`spi`	MOSI	GPIO 11
`spi`	CS	GPIO 10

Deploy the firmware

main.cppOpen in Schematik

#include <Arduino.h>
#include <SPI.h>
#include <SD.h>
#include <driver/twai.h>

void setupCan();
void setupStorage();

constexpr int GPS1_RX_PIN = 5;
constexpr int GPS1_TX_PIN = 4;
constexpr int GPS2_RX_PIN = 7;
constexpr int GPS2_TX_PIN = 6;
constexpr int PEER_ESP32_RX_PIN = 16;
constexpr int PEER_ESP32_TX_PIN = 15;
constexpr int MOTOR_SIG1_PIN = 17;
constexpr int MOTOR_SIG2_PIN = 18;
constexpr int CAN_RX_PIN = 14;
constexpr int CAN_TX_PIN = 21;
constexpr int SD_CS_PIN = 10;
constexpr int SD_MOSI_PIN = 11;
constexpr int SD_SCK_PIN = 12;
constexpr int SD_MISO_PIN = 13;

constexpr uint32_t GPS_BAUD = 115200;
constexpr uint32_t PEER_BAUD = 115200;

HardwareSerial gps1Serial(1);
HardwareSerial gps2Serial(2);
HardwareSerial peerSerial(0);

bool canStarted = false;
bool storageReady = false;

void setupCan() {
  twai_general_config_t generalConfig = TWAI_GENERAL_CONFIG_DEFAULT(
      static_cast<gpio_num_t>(CAN_TX_PIN), static_cast<gpio_num_t>(CAN_RX_PIN), TWAI_MODE_NORMAL);
  twai_timing_config_t timingConfig = TWAI_TIMING_CONFIG_500KBITS();
  twai_filter_config_t filterConfig = TWAI_FILTER_CONFIG_ACCEPT_ALL();

  if (twai_driver_install(&generalConfig, &timingConfig, &filterConfig) == ESP_OK) {
    canStarted = (twai_start() == ESP_OK);
  }
}

void setupStorage() {
  SPI.begin(SD_SCK_PIN, SD_MISO_PIN, SD_MOSI_PIN, SD_CS_PIN);
  storageReady = SD.begin(SD_CS_PIN, SPI);
}

void setup() {
  pinMode(MOTOR_SIG1_PIN, OUTPUT);
  pinMode(MOTOR_SIG2_PIN, OUTPUT);
  digitalWrite(MOTOR_SIG1_PIN, LOW);
  digitalWrite(MOTOR_SIG2_PIN, LOW);

  gps1Serial.begin(GPS_BAUD, SERIAL_8N1, GPS1_RX_PIN, GPS1_TX_PIN);
  gps2Serial.begin(GPS_BAUD, SERIAL_8N1, GPS2_RX_PIN, GPS2_TX_PIN);
  peerSerial.begin(PEER_BAUD, SERIAL_8N1, PEER_ESP32_RX_PIN, PEER_ESP32_TX_PIN);
  setupCan();
  setupStorage();
}

void loop() {
  // GPS streams remain independent. UART and CAN are available for comparison.
  // storageReady becomes true only when a formatted microSD card is installed.
  if (canStarted) {
    twai_message_t message = {};
    if (twai_receive(&message, pdMS_TO_TICKS(1)) == ESP_OK) {
      // Application-specific CAN message handling belongs here.
    }
  }
  delay(10);
}