[Little Dolphin Mobile Phone] Taishanpai 4G Internet Access Mini Mobile Phone

1. Demonstration
2. Project Description
A smart "phone" based on the Taishanpai system, capable of voice chat, 4G internet access, gaming, and video recording. The outer shell is 3D printed, and the back cover uses a LCSC color panel design.
3. Video Demonstration
I made a "phone" with a hundred yuan, can it shoot videos? Play Genshin Impact? Bilibili
4. Project Functionality

Adaptation A large 3.1-inch touchscreen
with reserved EC20 4G module mini PCIE interface, SIM card
onboard microphone
, reserved speaker, RTC interface
onboard CH343G TYPE-C debug serial port
onboard CH224K PD decoy chip, 12V output

5. Schematic Explanation
1. POWER
The EC20 module consumes a lot of power, and the 4G module has an independent power supply output. The 4G module power switch is controlled by the 4G_PWREN_H pin, i.e., GPIO0 PA5. When 4G is not needed, this pin can be set to a low level to save power.
Because the 4G module supply current is too large, using the computer's USB function will cause the Taishanpai system to restart indefinitely, so a PD decoy circuit is equipped. Using a mobile phone power adapter or PD power bank as input via the TYPE-C pin, the CH224K chip induces the PD to output 12V power to power the system. Here, CFG1, CFG2, and CFG3 are control system output pins. Adding a 24K resistor at CFG1 enables the PD to output 12V. Detailed configuration instructions can be found in the CH224K chip manual.
Directly using the Taishanpai power supply for the backlight would cause the screen to overheat; therefore, a separate power supply IC is used. The PWM output pin is GPIO0_C5 of the expansion port (this needs to be modified in the device tree).
2. EXP
expansion pins: Only the USB interface and GPIO0 PA5 are used here, mainly for communication with the 4G module. The USB interface communicates with the EC20 USB. GPIO0 PA5 is enabled at a high level and disabled at a low level.
The expansion board also connects to the Taishanpai via a 10mm pin, providing 12V, serial port, microphone, and speaker.
3. PCIE
EC20 circuit, referencing the Taishanpai network expansion board. Since the EC20 module mounting holes are blocked by the touch screen ribbon cable, CN6 is used to fix the EC20 module here.
4. LCD
circuit reference [1], mainly MIPI and touch circuit conversion.
5.
AUDIO/DEBUG provides CH343G serial to TTL, microphone, audio and RTC.
6 Circuit diagram description
The circuit diagram is shown in the figure below.
7 Outer shell and panel
The outer shell is 3D printed using 9000R material. The printing file is attached. Due to the thinness of the bottom cover, it cannot be 3D printed. The bottom cover V2.STL does not actually need to be printed. Here, two acrylic panels, one transparent and one colored, are superimposed. The transparent acrylic back cover can be matched with the outer shell slot. The colored acrylic plate has adhesive on the back and can be glued on top of the transparent acrylic cover.
8. Assembly Process
: Assembly Reference Video - DIY Taishanpai Small Mobile Phone Assembly
9. Usage Reference:
Detailed Tutorial - Development Board Manual


- LCSC Development Board Manual [LCSC Taishanpai RK3566] Development Board - Feishu Cloud Documents (feishu.cn)


Mobile Phone Making Process [Fat Girl Mobile Phone] Practical Project Materials - Feishu Cloud Documents (feishu.cn)


Android System Compilation [Android] System SDK Compilation - Feishu Cloud Documents (feishu.cn)


System Image Burning [Download] Image Burning - Feishu Cloud Documents (feishu.cn)


10. Software Debugging
Code Patch Download:
Zhiwu Xiaobai/TSPiPhoneEXT - Gitee.com
11. Material Reference:



Material
Model
Link (For Reference Only)




4G Module
EC20
https://m.tb.cn/h.g0cwnmI2zW8jL4I?tk=se1zWrEOK 22


Speaker
2209
https://m.tb.cn/h.gZqOZijCgpquogw?tk=7byiWrEmmut


Touchscreen flex cable
6P 6cm same side 0.5mm
https://m.tb.cn/h.g0vaMhBpkwiYjat?tk=QEFUWrEmfey


Screen flex cable
31P 6cm same side 0.3mm
https://m.tb.cn/h.gZqMBM7sMdxqR3q?tk=xne8WrEM3YR


Extension flex cable
39P 6cm same side 0.3mm
https://m.tb.cn/h.gZqMBM7sMdxqR3q?tk=xne8WrEM3YR


Debugging serial port
CH343G SOP-16
[ Links to various webcams and


related products are included, but are not translated as they are not part of the product description . ] https://m.tb.cn/h.gcqOhk6OtbETlWD?tk=Q4VYWGh1BGy Screw CM2*5 Head Diameter 5


























https://m.tb.cn/h.g1F0Og2GhkunkTD?tk=YKR4WGhbruw


Other
references BOM




12 Image display
13 Version update notes
2024-4-21 V2 version optimizes screen interface layout
2024-5-28 V3 version adds screen backlight circuit IC and optimizes screen backlight heat generation
Project reference
[1] Taishanpai 3.1-inch screen expansion board - integrated power supply, audio, serial port, RTC - JLCPCB EDA open source hardware platform (oshwhub.com)
[2] LCPCB Taishanpai development board 39Pin_Hub2.0_Ethernet expansion board