Ever Modular V1

For as long as I can remember, I have been fascinated by the idea of designing and building small RC cars with unique and versatile designs. This project focuses on creating a compact and adaptable PCB specifically for small RC cars. The goal is to make a pcb that can be integrated into various RC car designs, making it both practical and educational for anyone interested in electronics and robotics.

# DEMO VIDEO
Demonstration video for Ever Modular V1



This is my first prototype and will demostrates as a base for my future project!

The PCB incorporates the BQ24074 for efficient battery management, a DRV8833 motor driver to control two DC motors, and an ESP32-C3 microcontroller equipped with boot and reset buttons for convenient programming and operation. Additionally, a buck converter is used to step down VIN/5V to 3.3V, ensuring stable power delivery to the microcontroller and peripherals. This combination of components provides a versatile and educational foundation for exploring RC car electronics, programming, and motor control.

External components needed:
N20 motors x2
Li-ion battery 3.7v x1
TFT display 12 pins x1

Boot button ESP32 c3:

🔌 Strapping pins and boot mode (from the datasheet)

📌 In this table “1” means HIGH, “0” means LOW at reset. documentation.espressif.com

So during Joint Download Boot (the ROM bootloader mode used to flash firmware), the required conditions are:

• GPIO2 is HIGH
• GPIO8 is HIGH
• GPIO9 is LOW ✨

This matches your statement — and exactly what the datasheet shows. documentation.espressif.com

🧠 But what does that really mean in practice?

➤ GPIO9 is the only one you actually need to toggle

GPIO9 is the only strapping pin you actively need to pull LOW when you want the ESP32‑C3 to enter download mode. That’s why dev boards only give you a BOOT button on GPIO9 plus a RESET button. documentation.espressif.com

➤ GPIO2 and GPIO8 don’t need buttons

• They must be HIGH at reset for Joint Download Boot, but:
  • Both have internal weak pull‑ups
  • You can add external pull‑ups (recommended) so they stay HIGH
  • They do not need buttons or switches to pull them low intentionally

The datasheet even says:

GPIO2 actually does not determine SPI Boot and Joint Download Boot mode, but it is recommended to pull this pin up due to glitches. documentation.espressif.com

So GPIO2 is HIGH for both modes anyway; it doesn’t decide the boot type — it just helps keep things stable.

🧠 Why the table says GPIO8 = HIGH for Joint Download Boot

In the datasheet table the download mode line shows GPIO8 as 1 (HIGH) — meaning it must not be pulled LOW at reset if you want reliable download mode. documentation.espressif.com

That’s why many designs add a pull‑up resistor on GPIO8 too — to ensure it’s not inadvertently LOW when you’re trying to enter download mode.

USBC + ESD

• Previous project from: Little Companion Robot | P1.Schematic2 | EasyEDA Pro - V2.2.45
• USB_DP → D+ → IO19
• USB_DN → D− → IO18

Thanks for the feedback and recommendation from the community, I changed from using TVS protection diodes to USB 2.0 protection IC for a stronger protection.

USBC Schematic and Layout Review : r/PrintedCircuitBoard

【ESP32-S3】1.69寸触摸屏迷你控制器~ - 立创开源硬件平台

BQ24074

• BQ2407x Standalone 1-Cell 1.5-A Linear Battery Charger with PowerPath datasheet (Rev. N)
• Using BQ24074RGTR

Diode used SS34 for 3.7v battery towards BQ24074RGTR

Pin 13 and 8 is checked and proof.

68532e9eb06c6.png (10079×7128)

BQ2407x Standalone 1-Cell 1.5-A Linear Battery Charger with PowerPath datasheet (Rev. N)

EasyEDA(Standard) - A Simple and Powerful Electronic Circuit Design Tool

CHG and PGOOD (checked and proof)

• CHG - charging status (Whether it is fully charge or not yet)
• PGOOD - weather is good to power up system
• Use led to indicate, connected to 3.3v and resistor

EP, CE#, VSS (checked and proof)

connected to gnd

ISET - Used for setting the maximum battery charging current

• connect a resistor to gnd
• 910 ohms connected → 0.98A charge current

ILIM - limits maximum current drawn from USB / VBUS

• resistor between gnd
• 1.5k ohms connected → 1A current pass through from USB

TMR - sets the maximum charge duration for the battery (Safety timer)

• resistor between gnd
• Connected to 36k to achieve about 3 hours charging time

ITERM - prevent overcharging

• resistor between gnd
• connected 6k resistor for 10% capacity

OUT - main power output

• Voltage follows VBAT when USB is disconnected (battery supplies system)
• When USB is connected, voltage is regulated by the charger (VBUS – charge circuit)
• Voltage follows VBAT when USB is disconnected (battery supplies system)
• When USB is connected, voltage is regulated by the charger (VBUS – charge circuit)

EN1 and EN2

• connect to out is the bets for now for normal charging
• https://chatgpt.com/s/t_694e221f8620819195b2bd24b4f862e9

My Work (Everything is proven) BQ24074

Buck convertor TLV62569DBVR

• Same as previous project
• Used the two resistors to make sure is 3.3v output

ESP32 c3

ESP32-C3-WROOM-02 N4 chosen

• Cheaper, more gpio, simpler design
• No usb to uart needed just connect directly with gpio 18 and 19 according to datasheet

Espressif Centralized Documentation Platform (CDP) | Espressif Documentation

sch_esp32-c3-devkitm-1_v1_20210

IO9 - Boot

EN - Reset

Explain why EN should connect to the capacitor!

https://chatgpt.com/s/t_694f62087f1c8191b6d8267a706b2037

RGB and LED

• From previous project
• Rgb led used 5v meanwhile led is for checking if buck convertor works properly

Drv8833

• Using drv8833pwr

DRV8833 Dual H-Bridge Motor Driver datasheet (Rev. E)

JLCEDA(Standard) - A Simple and Powerful Electronic Circuit Design Tool

[已验证]DRV8833电机驱动模块 - 立创开源硬件平台

Experiment before continuing:

• Find out which gpio pin to use
• Find out pin for motor
• Find out all pins that required to use

STBY → NSLEEP → 3.3v

NC → Don’t care at all

AISEN and BISEN need to be connected to gnd!

https://chatgpt.com/s/t_6950aadf89e88191bff77e11028a25e6

VCP → connect to VM through 10nF capacitor (By official datasheet and oswhub)

VIN → VIN (3.7v/5v)

AOUT1/2 & BOUT1/2 → Motor output

AIN1/2 & BIN1/2 → GPIO connect