Q302 Desktop Multimedia HiFi Host + Charging Station

Updated video links:
4. Q302 desktop multimedia terminal final assembly video: https://www.bilibili.com/video/BV1Cm4y1J7bF
3. I have to finish burying the hole I dug myself during the hardware debugging of the Q302 multimedia terminal. https://www.bilibili.com/video/BV1Zo4y1z7vi/
2. Immersive hardware debugging, Q302 desktop multimedia terminal Part-2 debugging USB decoding and amplifier circuit https://www.bilibili.com/video/BV1fY4y1278G/
1. Q302 desktop multimedia terminal Part-1 trailer [Desktop HiFi amplifier + gallium nitride fast charging + high-definition sub-screen] https://www.bilibili.com/video/BV1o84y1p7te/
Project description
This project plans to create an integrated desktop multimedia terminal, the functions include: 1. Dual-channel desktop HiFi amplifier (three input modes 3.5mm, USB decoding, Bluetooth); 2. Desktop charging station, support wireless charging; 3. Multimedia display terminal, support display of more media information, and can even be used as a sub-screen. 4. Built-in AC-DC power supply solution, refuse external big brick adapter.
5. Must look good! As a desktop terminal, this is the most important.
 
Open source agreement
GPL3.0.
 
Project related functions
1. Two-channel desktop HiFi amplifier;
support advanced 3.5MM headphone jack;
support USB audio decoding;
support Bluetooth audio input;
maximum support 30W*2 audio output.
2. Desktop charging station
(the gallium nitride part has changed its design because the transformer needs to be customized, the protocol chip is not easy to buy, and it is difficult for everyone to reproduce it. It is decided to change to a general solution to facilitate everyone to reproduce it)
Expanded support for wireless charging.
I thought there would be no pitfalls in this part, but there are really many pitfalls in the actual production. The gallium nitride solution I chose at the beginning was also made by netizens, but the high-frequency transformer needs to be customized. This is okay, you can buy it with money. Second, you can't buy a 65W fast charging protocol chip, only a 20W one, so what's the point of gallium nitride? Third, the voltage of the gallium nitride power supply is not clean, and the noise is relatively large, resulting in serious background noise in the amplifier part. Then I started to test the ordinary switching power supply. I tried several cheaper ones and the results were not ideal. I almost gave up. If it weren't for the limited space in the chassis, I would have wanted to use the ring bull directly. When I made the LM3886 amplifier before, the effect of using the ring bull was very good. Finally, I accidentally tried a monitor power supply that I have on hand, and the effect is okay. Let's do it this way first, and think of a better solution later.
The common power supply of the wireless charging part and the power amplifier part will cause the problem of increased background noise when the wireless charging is working.
3. Multimedia display terminal.
Support HDMI audio and video input;
support 40Pin-30Pin-iPad3/4EDP screen driver;
extract audio information to the power amplifier module.
NCS8803 video signal processing solution.
The debugging of this part is the most difficult part, which wasted too much of my time. At first, the screen driver could not be driven, and later the HDMI data was not connected. In addition to the board for participating in the event proofing, I closed the board twice by myself, and finally only adjusted one board. The success rate was too low. I once suspected that there was a problem with my own board drawing skills. The cost of the back and forth completely exceeded the cost of buying a finished board. If a friend wants to replicate this project, it is strongly recommended to buy a finished board instead of this function. The corresponding 3D printing file also supports the most common dual mini HDMI driver board that can be bought, so don't compete with yourself.
4. It must look good!
As a desktop terminal, this is the most important one. The shell is planned to use Jiali Chuang's CNC aluminum alloy design, cathode oxidation surface treatment. In order to be compatible with wireless charging, the top is 3D printed, which is also a pit for myself. The 3D printed shell will be deformed to a large extent after a long time (about 1 month), resulting in the parts combined with the aluminum chassis not being able to fit together tightly (it can be done when it is just printed). Later, there are problems such as the buckle breaking and the screws cannot be installed normally.
 
Project attributes
This project is the first public and is my original project. The project has not won any awards in other competitions.
Although it is not excellent, it is prohibited to reproduce it for commercial purposes.
 
Project schedule
Planned schedule:
Circuit design in January-February;
Circuit debugging in March;
Shell design in April;
Finished product in May-June;
Actual progress:
20230211, PCB design completed, SMT application submitted. Start shell design.
20230222, 70% of the shell design is completed (the main CNC structure is completed, and the 3D printing structure is in progress);
20230222, PCB proofing is completed and debugging has begun (USB decoding, dual-channel power amplifier, and integrated power supply module have been adjusted);
20230222, the USB decoding program has been completed.
(The first draft of the 3D appearance is still being modified, and it is being modified while debugging. This version has been abandoned. In fact, I still like this version the most, but this time it was made based on an existing product. I was worried about the problem of appearance infringement, so I finally gave up this version. It's a pity)
20230310, hardware debugging is in progress .
The appearance design has been updated, using a contrasting color design, the lower part is an aluminum alloy oxidation process, and the upper part is 3D printed (mainly for wireless charging).
In addition, the display part adopts a detachable design to facilitate the needs of different users.
The effect picture after assembly
20230415, the preliminary assembly and debugging of the hardware (the CNC shell is not yet completed, and it is now a 3D printed version)
 
Design principle
 
The USB decoding part adopts the STM32F4+WM8978 solution;
the power amplifier part adopts the TPA3116 solution;
the HDMI part adopts the NCS8803 solution;
the power management part adopts the LM5122 solution;
 
Software description (the program source code has been uploaded as an attachment and can be downloaded directly. Please do not use the open source code for commercial purposes.)
 
Physical display
1. Overall effect picture
2. Front TFT screen debugging-
speaker panel. Two 3-inch full-range speakers are used, the upper middle part is the display screen, the middle part is the volume adjustment, and the lower half is the sound source channel selection.
3. Deep space gray aluminum alloy CNC process (the 3D printed top cover has been deformed)
4. Portable screen with detachable parts
However, the V1.0 motherboard is still too complicated, and it is not recommended to reproduce it. If necessary, you can consider the simplified version of V2.0.
10. The front panel of this version
11. The back of the upper cover is an integrated wireless charging module
 
Design considerations (big pitfalls have been found)
1. The STM32 microcontroller VCAP pin forgot to connect a capacitor.
2. The MUTE mute control signal is only connected to the Bluetooth module, affecting other channels. The V2.0 version has been connected to the microcontroller.
3. The gallium nitride power supply has a large noise and is not recommended. The ordinary switching power supply used later is used for power supply. In addition, when the wireless charging part is working, it also has a certain interference with the audio amplifier part, which significantly increases the background noise.