Modular desktop clock (M.2 core board, PCI-E 1x expansion board)

Station B video link 1: https://www.bilibili.com/video/BV1Um4y1F7x2/
Station B video link 2: https://www.bilibili.com/video/BV1Jd4y1i7Qp/
Video collection link: https://space. bilibili.com/510334379/channel/collectiondetail?sid=831107
View volume as of 2022-11-23:
The question requires
modular design and multi-channel desktop clock;
for modular design ideas, refer to PC motherboards that can carry different types of CPUs and graphics cards , sound cards, etc. This design idea allows the mainboard to be equipped with different core boards (M.2) and function boards (PCI-E 1X) with different functions can be inserted to achieve flexible scalability.
Question analysis
1) Timing mode:
GPS, BD, WIFI, NB network, etc.
2) Modular circuit design, including:
1. One universal motherboard:
supports the insertion of one core board (M.2 interface) and
four functional boards (PCI -E 1X),
supports lithium battery charging,
each board is independently powered (3.3V),
has an onboard 0.96TFT display (optional) and encoder interface.
2. One M.2 interface core board:
the STM32F103CBT6 chip used this time, the main control chip can be replaced later.
3. Four functional boards for the PCI-
E WeiXue 1.8-inch TFT, or other SPI serial screen.
3.2. CARD3: ​​Signal source input board, integrating GPS, BD, WIFI, NB and other time source input methods.
Design progress description:
[Updated on 2022-10-07] Completed the relevant 3D printing model design.
[Updated on 2022-09-24] The debugging of the display board is completed, and the functions are implemented:
getting the time from the Tencent server;
getting the weather;
getting the number of fans of station B;
2022.07.30 Completed the design
2022.07.26 Basically completed the school time board PCB
2022.07.24 Basically completed Time board schematic diagram and display board schematic diagram
2022.07.23 The mainboard schematic diagram is basically completed and the mainboard PCB layout is completed.
2022.07.22 The core board PCB (remaining power supply) is basically completed; continue to advance the mainboard schematic diagram.
2022.07.21 Complete the core board schematic diagram.
PCB design instructions
1. The bus
M.2 is converted to the PCIE bus. The power pins are as compatible as possible with the original definition. Other IOs are divided into serial ports, I2C, SPI, etc. and are allocated to four functional boards.
Each functional board has an independent serial port (1/2 share one channel). The functional board has an independent status indicator light to the main board.
IO ports are multiplexed on different boards. Because the current core chip IO is limited, they cannot be used exclusively.
2. The power supply
core board has DC-DC power supply of 3.3V, and
the functional board AMS1117 provides high current power supply. It also has 5V direct input, using the original protocol 12V channel.
3. Other
onboard OLED interfaces and rotary encoder interfaces can be customized for use.
Partial code description
1. Obtain weather and B station fans
2. Obtain time
3. WiFi configuration
physical picture update:
(Core board)
(Function board)
(Motherboard)


Physical display instructions
(Board card collection)
(Assembly effect)
(Display effect)
Description of known bugs:
Only two SMTs can be made in one batch, only the motherboard and core board. The expansion board was proofed by myself, without a chip attached, and was first compatible with an original screen.
The power supply part of the onboard PCI-E uses the AMS1117-3.3 solution. This solution is invalid when using battery power supply and cannot reach the input voltage.
External USB power supply is OK, please pay attention to the welding of jumper resistor R21.
There is one less M.2 fixing hole. The core board needs to be installed with a 3D printed bracket.
The display module temporarily uses the original screen module. The PCB file and program have been uploaded separately. When making it, please note that the LCD may not be easy to buy.
In order to reduce the thickness, the WIFI module chooses flying wire connection.