Advanced single chip microcomputer -- development of PCB (2)

Previous review

《 Advanced MCU —PCB According to the development of gourd painting ladle （ One ）》
After about a week ,PCB Here we are , Have to say , Li Chuang's efficiency is really high , Or by air .

The components are basically in place , Here is BOM detailed list ：
Let's talk about a little knowledge first .

Minor modifications

The work of the boss in front uses three buttons , In fact, it still takes up more space , So I changed three buttons into a wave wheel switch

The schematic diagram replaces the original three switches , Up and down is SW1 and SW3, Pressing down is SW2.

This will give the poor PCB Make room , Although I don't know what to put .

Then the boss's board uses IIC Communication screen , In fact, the software supports SPI Of , So I debug and modify the hardware on the development board SPI, Then... In the schematic diagram IIC, Change it to SPI Interface


SPI The refresh rate of is still much higher .

Schematic analysis

The watch is powered by batteries , So you need a charging circuit .

Charging schematic diagram

among 5v originate USB Interface , And then through tp4057, Convert to about 4V The voltage of , to VBAT Charge , Charge the battery , When charging LED1 It will light up , Then as the power increases ,LED2 Brighten ,LED1 Darken , Finally, it is fully charged ,LED2 bright ,LED1 destroy .

Let's take another look at the one button boot circuit .

Probably the principle is also learned from the Internet , This one button power on circuit , Aim long press the button , send VBAT+ Turn into VBIN, Release the button , The circuit remains .
The principle is when SW2 When pressed ,Q1 Conduction , SCM power supply , The system gives PWR_ON Power supply ,Q2 Get through , Release the button again ,VBIN It can also continuously output VBAT+ 了 . Maybe you're not quite right , That's about it

There is also a voltage stabilizing circuit , Continuously and stably output the battery voltage to VCC

Other parts will no longer be , Just some IIC Communication with sensors , Barometer sensor is used , Gyroscope and clock chip .
In fact, every part , There are more specific examples on the Internet , Search for yourself , Can also piece together a product

Step by step , No bullshit

Through the previous general study , I see, on this circuit , Which functions require which components , So the beginning of welding , Is to weld the smallest system board , Immediately welded MCU, Then crystal oscillator and capacitor , The final will be STlink The circuit is well welded , You can burn and run the program .

So the first thing is to weld MCU And peripheral circuits

Then weld the debugging circuit

Then weld the display interface , Plug in the small screen , Smooth words , The program can run , The screen will display normally .
No photos were taken during the process , Sorry

Then weld the switch , You can operate two functions , But confirmation is not enough , Because the front one button boot circuit , Not welded yet ,SW2 Pressing is unresponsive .

Then weld the charging circuit and USB Socket , Then turn on the power and test the voltage at both ends of the battery , belong 4V about , It's almost there

Then weld the voltage stabilizing circuit and the battery , Then weld the one button start-up circuit , You can start the watch independently .

Red light is displayed when charging

The display is full of green light

Finally, weld the two sensors , Pay attention to at least welding the gyroscope and temperature and humidity , Retest , Otherwise, there will be problems .
Temperature and humidity display

gyroscope

Finally, weld the clock chip , It's almost finished . Install another strap .

At first, I thought that a man on the salted fish would sell this work for more than 300 , It's quite expensive , Until I welded half , To realize , If only it were welded manually , Sell you more than 300 , What a conscientious seller

Step by step test , Sometimes there is faulty welding , worry .

But try a few more times , Finally, it was engraved by me .

Supplementary information

Slurry temperature

About the use of this tin paste , At first, blow the medium temperature tin slurry with an air gun , The temperature is set to three Baidu , That must be possible , But I found that when welding the switch , If you don't pay attention to the switch, it will blow out of shape , Then set the temperature to 220 degree , Cash back is also possible , Plastic inserts won't deform anymore , So you don't have to buy low-temperature tin slurry , Of medium temperature tin paste welding patch LED No problem .

LED The direction of

Many packages are like some 0603、0805 And other packaged SMD LEDs will have... At the bottom ”T” Glyph symbol ,“T” One side of the horizontal is the positive pole , On the other side is the negative pole

Strap installation

I sewed this piece by hand , I wonder if there is a better strap , Or it's cool to make an ear that can directly install the watch strap .

Conclusion

It's not difficult to make this thing , The software and hardware are open source , I'm still one more step , I drew it myself PCB, Some devices have been changed , But nothing at the core moved .
The process is more time-consuming and patient , Because it's mainly waiting for express delivery .

There's no need to do nucleic acid today , A quiet day , I hope to hear the good news that there is no new news in the society today , I don't want to pedal in three rounds .