【MCU】ESP32 Minimum System Board Project

1. General Overview
      ESP32-WROOM-32E-N8 is a module designed by Espressif Systems, a domestic company. Based on this module, the minimum system board is designed, all IO pins are brought out, and OLED display, buttons and three-color light peripherals are added. C/C++/MicoPython can be used for development, which is convenient for quick entry development and learning. It is compact and exquisite with complete functions.
Figure 1-1 ESP32 minimum system board 3D model Figure
 
1.1 Pin distribution
Figure 1-2 ESP32 minimum system board pin distribution Figure
 
1.2 Onboard resources
Figure 1-3 ESP32 minimum system board onboard resources
Main control chip: ESP32-WROOM-32E-N8 Module
power interface: TYPE-C
Function buttons: Reset button and Boot button
Display function: Power indicator light display, two three-color light displays, four-wire OLED screen display
Debug interface: CH340 serial port debugging
External pins: Full-function pins are brought out for easy expansion of connections;
 
1.4 Advantages and features
Figure 4-1 Minimum system board size diagram
The board is small and exquisite, with a size of 50mm*74mm (1968.5mil/2913.4mil);
supports development using C/C++/MicoPython language, which is convenient for quick learning;
provides TYPE-C serial port for easy development and debugging;
onboard reset button and Boot button;
supports 2.5GWiFi and BT/BLE wireless communication;
has two three-color lights and a four-line OLED display to meet the development and learning needs of beginners;
uses Jiali Chuang's high-quality PCB and Li Chuang Mall genuine components to ensure product quality;
 
2. Main control introduction
 
2.1. ESP32-WROOM-32E-N8 module introduction
 
Built-in ESP32-DOWD-V3 chip, Xtensa dual-core 32LX6 microprocessor, supports clock frequency up to 240Mhz
448KB ROM
520KB SRAM
16KB RTC SRAM
N8 represents the module with built-in 8M Flash
Working voltage/supply voltage: 3.0~3.6V
The PCB onboard antenna
integrates traditional Bluetooth BT, low-power Bluetooth BLE and Wi-Fi
 
2.2. ESP32 module internal circuit diagram
Figure 2-2 Module internal circuit diagram schematic diagram
 
2.3. Module schematic Notes
To ensure that the power supply of the ESP32 chip is normal when it is powered on, an RC delay circuit needs to be added to the EN pin. RC is usually recommended to be R=10K and C is 1uf. The specific value is adjusted according to the power-on timing of the module power supply and the power-on reset timing of the chip.
The maximum operating voltage of the module is 3.6V, and it cannot be directly connected to 5V for power supply.
GPIO34~39 are input-only pins. These pins do not have built-in pull-up or pull-down resistors, and they cannot be used as outputs.
ESP32 has 5 strapping pins, IO12, IO0, IO2, IO15, IO5. Among them, IO5 and IO15 must be high level when starting, and IO12 must be low level. These modules have been set, and the state cannot be forcibly changed by external pull-up or pull-down resistors, otherwise it will not start normally.
The supply current of the external power supply needs to be at least 0.5A. It is not recommended to use a low-current LDO to drive the module.
 
2.4 ESP32-WROOM-32E-N8 module product introduction
Brand: ESPRESSIF Lexin
Manufacturer model: ESP32-WROOM-32E-N8
Product number: C701342
Package: SMD, 18x25.5mm
Data sheet: Download file
Product gross weight: 2.49 grams (g)
Packaging method: Tape
Purchase link: LiChuang Mall purchase link
 
3. Engineering design
 
3.1. Power supply circuit
      The ESP32-WROOM-32E-N8 module requires a 3.3V voltage supply. The power supply uses a TYPE-C interface to input 5V, and then outputs 3.3V to the chip through the AMS1117 step-down chip. The maximum output current of AMS1117 is 1A, which is enough to meet the power supply requirements of the module.
Figure 3-1 Power supply circuit
 
3.2. Main control circuit
      All available pins of the ESP32-WROOM-32E-N8 module are brought out, and a 100nf filter capacitor is added to the power input part of the module to provide a stable power input for the module.
Figure 3-2 Main control circuit
 
3.3 Serial port download circuit
      The module communicates and downloads programs through the TYPE-C interface and the CH340 serial port chip. Since the ESP32 chip has different startup modes, the automatic download function is realized by using two transistors, and there is no need to manually switch the level to enter.
Figure 3-3 Serial port automatic download circuit
 
3.4 Four-wire OLED screen interface circuit
      is connected to the OLED screen through a 2.54*4P female header. A 4.7K pull-up resistor is added to the IIC data bus, and a 100nf capacitor is added to the power input part to stabilize the power supply.
Figure 3-4 OLED display interface circuit
 
3.5. RGB three-color light circuit
      Two RGB three-color light peripherals are added, which can be used as a simple test of the module.
Figure 3-5 RGB three-color light circuit
 
3.6. The button circuit
      leads out a reset button and a BOOT button. After the module is started normally, the BOOT button can be used as a normal button. Both buttons are added with RC delay circuits to complete the button debouncing and provide simulation for the startup timing of the EN pin.
Figure 3-6 Button circuit
 
3.7. The expansion interface circuit
      leads out all available interfaces through two 2.54*12P pin headers, and adds 2.54*2P pin headers to expand the power supply part to facilitate the use of subsequent projects.
Figure 3-7 Expansion interface circuit
 
3.8. SCH_ESP32 minimum system board
Figure 3-8 Overall schematic diagram
 
3.9. PCB layout It is recommended that
the main control module be placed in the middle of the board frame, and the antenna should not be placed inside the board frame to avoid interference.
It has a certain space capacity. The OLED display is connected through a female header. The screen printing on this side of the display only indicates the size and the position of the screws around it.
The expansion pins for placing components inside the screen printing are placed on both sides. Pay attention to leaving a position for the screen printing
to place screw holes around. At the same time, a prohibited copper plating area should be placed around the screw holes. Place the short-circuit
filter capacitor nearby. The power supply must first pass through the capacitor and then to the chip.
 
3.10. PCB wiring recommends that
the power line be set to 30mil, because the ESP32 module requires a large current. The signal line is 10mil, that is, the top layer
can used as the main routing. If it cannot be passed or needs to be routed a long way, switch to the bottom layer through the via for
connection. Straight lines are preferred during routing. Do not route at right angles or sharp angles. Route horizontally, vertically, and symmetrically to keep the design beautiful.
During the wiring process and after the routing is completed, place GND vias appropriately for heat dissipation and ensure that the return path of the current is as short as possible.
 
3.11. Silkscreen copper plating suggestions
Figure 3-11-1
Add silkscreen logo buttons and external pin information to the top copper plating;
add teardrop effects after drawing and adjusting the PCB to make the board more beautiful and stable;
add JLCJLCJLCJLC to specify the guest editing position under the components to make the board beautiful;
 
4. Programming and development
 
4.1. Development environment selection
      ESP32 can use MicoPython/C/C++ language for development and learning. When using MicoPython language development, it is recommended to use Thonny IDE, and when using C++ language development, it is recommended to use Arduino IDE. C language development is recommended to use VScode+IDF plug-in for development.
4.2. Download program
      In the above development environments, the download interface has been integrated. After writing the code, you can download and debug it by yourself. In addition, if you want to download other people's firmware, you can use Espressif's official flash burning tool, which I will place in the attachment.
Figure 4-2 Download tool
 
5. Physical verification
 
5.1 Bill of materials
Serial number
Name
Device bit number
Parameter
Quantity
Package
Item number
1
TYPE-C interface
USBC1
TYPE-C-31-M-12
1
USB-C_SMD-TYPE-C-31-M-12
C165948
2
Resistors
R5, R1, R4
1K
3
R0805
C17513
3
R2, R3
4.7K
2
C269746
4
R6, R7, R8, R9
10K
4
C17414
5
LED light
LED3
red light
1
LED_0805
C84256
6
LED1, LED2
RGB tricolor light
2
LED-ARRAY-SMD_4P-L1.6-W1.5-BR_XL-1615RGBC-RF
C965840
7
Capacitors
C2, C4
10uf
2
C0805
C15850
8

C3、C5、C1、C6、C7、C9、C8

100nf
7
C38141
9
Buck chip
U1
AMS1117-3.3
1
SOT-223-3_L6.5-W3.4-P2.30-LS7.0-BR
C6186
10
Female row
U2
2.54*4P
1
OLED-TH_L27.8-W27.2-P2.54_C9900033791
C5248080
11
SMD button
SW1、SW2
two-foot SMD button
2
Key_SMD_3.6x6.1x2.5
C118141
12
Serial port chip
U3
CH340C
1
SOP-16_L10.0-W3.9-P1.27-LS6.0-BL
C84681
13
ESP32 module
U4
ESP32-WROOM-32E-N8
1
WIFI-SMD_ESP32-WROOM-32E
C701342
14
Pin header
H1, H2

2.54*12P

2
HDR-TH_12P-P2.54-VM
C2840012
15
H9, H6, H8, H7

2.54*2P

4
HDR-TH_2P-P2.54-VM-1
C124375
16
Transistor
Q1, Q2

SS8050

2
SOT-23-3_L2.9-W1.3-P1.90-LS2.4-BR
C2150
 
5.2. Device welding
      On the PCB editing page of Jiali Chuang EDA professional board, select tools, open the welding auxiliary tool to help quickly locate the device position.
Figure 5-2-2 Bottom welding diagram
Welding precautions
First weld TYPE-C, make sure that TYPE-C has no welding short circuit, then weld the others After
the SMD components are welded, weld the plug-in pin and mother row
Before welding the chip, use a multimeter to measure whether there is a short circuit, place the burnt chip
 
5.3. Finished product display
Figure 5-3-2 Actual Figure 2