TimerV2

#A simple timer with no special functions. It can be used as a clock (the power consumption is a bit high).  

## Key components & features

###STM32 master control, SPI FLASH, FATFS file system, soft MP3 decryption (spirit DSP), RX8025T (RTC), NS4168 (I2S amplifier).  

*Standby mode wakes up once every minute to update the time, and timer mode wakes up once every second.  

*All key presses interrupt wake-up.  

*Low power consumption, standby is about 600uA, of which the screen consumes about 200uA. If you have time, adjust it again, and it should be able to drop further.  

* Soft decryption of MP3 can be said to occupy very low resources. The minimum RAM required is only about 18KB. However, please note that this is a commercial solution and is not open source .  

*FATFS file system.  

*16MB SPI FLASH is enough to play several songs.  

*RX8025T clock, accuracy is pretty good.  

*JSON format configuration.  

*DFU bootloader updates firmware.  

*MSC (U disk) method to update music files.

The menu supports displaying up to 5 pieces of music. It may be changed to a dynamic list later, but it is of little significance. The FLASH is only 16M, so it cannot play a few songs.

U disk effect:

## Known issues

If USBLC6 is used incorrectly, the 1.5K resistor on the DP end will leak through it to the 5V power supply line when the USB is not connected, causing leakage and USB insertion detection errors. This can be avoided by turning off the USB_EN pin in the software. To save trouble, I just cut off the fifth leg of this piece of material.  

The baud rate of the I2S peripheral must be set to 1/2 of the actual MP3 baud rate for normal playback. The reason is not yet clear.  

The storage function of this JSON library is not very easy to use. I have been struggling for a long time and I don’t know how to store int, so the volume is also stored as a string.  

The interrupt output setting of RX8025T seems to be a little different from the manual, which may not be very scientific, anyway it works.  

The screw holes on the bottom shell of the 3D shell are a little smaller. It will be better to use a 3MM drill bit to drill them; the top cover may automatically have countersunk holes (LCEDA bug, said to be fixed in version V1.8), which needs to be canceled in the setting .

## Notice  

This MP3 soft solution solution is partly non-open source. I am using a limited demo here. Please do not use it for commercial purposes. If you are interested, please contact the provider SPIRIT DSP yourself. There are relevant contact information in the library file directory.  

## The code is here:

https://github.com/lingex/TimerV2.0