You can make this simple player using 8051 microcontroller. Although the sound quality is not so good but its ok for diy. This wav player uses AT89C2051 microcontroller as CPU. The nokia 3310 LCD display is used here.
This player did not use the FAT file system, due to the limited RAM in AT89C2051. It just read the SD card sector. Also we should read 512bytes at a time, but with 128byts in this cpu we are playing the file while reading the card. Music files are 32KHz sampling rate WAV files. The source code is written in keil C.
Circuit DiagramComponent Details:
- R1, C1 form the LCD power-on reset circuit.
- R2 ~ R4 is a pull-up resistor, although 2051 of the IO has an internal weak pull-up, but three IO interface and keyboard interface of LCD re-use, need to pull a little stronger.
- R5, R6, Q1 output of the inverter composed of OC, when the SCE is high, the transistor turns on, enabling the keyboard, LCD communication suspension; when SCE is low, LCD communication enabled, the keyboard is disconnected. Note that the figure did not add around two key blocking diode, Do not press, or show cause confusion.
- R2 ~ R6 do not significantly change the parameters, these parameters are calculated to be a more appropriate value.
- Crystal, C3, C5 nothing to say, these are important to a microcontroller.
- R7, R8 is the P1.0 and P1.1 pull-up resistor, as the two ports are open-drain output.
- R9 ~ R24-type composition of R2R DAC, select 50K/100K since 2051 with output high load ability, resistance is too small will result in deterioration of DAC linearity. This resistance is best to use 1% metal film resistors, in order to improve the DAC linearity. 50K resistor non-standard resistance, where resistance in parallel with the 51K and 2.7M instead.
- C6 is a high-frequency filter capacitor to reduce the DAC output of the high-frequency noise.
- C7 is the output coupling capacitor, connect LINE OUT output terminal, the output impedance is high, 50K, can only take power amplifier or powered speakers. If the headset connected, need to add a zoom, you can do with the op-amp follower, or TDA2822 amplifier IC, can bring a small loudspeaker.
AT89C2051 Based SD Card Wav player 1.0
AT89C2051 Based SD Card Wav player