BadUsb USB Microcontroller ATMEGA32U4 Keyboard Development

Sound card, also called audio card (called sound effect card in Hong Kong and Taiwan), is the most basic part of the computer multimedia system, and it is a kind of hardware that realizes the mutual conversion of sound wave/digital signal. The basic function of the sound card is to convert the sound signals from microphones, tapes, and CDs, and output them to sound equipment such as headphones, speakers, amplifiers, and recorders, or to send out the sound of synthetic musical instruments through the digital interface of music equipment (MIDI). The block sound card is called ADLIB Magic Sound Card, which was born in ADLIB AUDIO Company in the UK in 1984. It can be said that ADLIB is a veritable "father of sound cards". Of course, the technology at that time was still very backward, and there were many deficiencies in performance. Take this sound card as an example, it is monophonic, and the sound quality is simply terrible, but there is no doubt that its birth, pioneering It is the first of its kind in computer audio technology [2].
What really brought the sound card into the personal computer field was the Sound Blaster "Sound Blaster" invented by Mr. Shen Wangfu, chairman of Singapore Innovation Corporation. This sound card caused a stir at the time. Some people think that this is a good start, because the PC can finally "talk", and think about what the multimedia PC will look like in the future. But others thought it was just a farce (because the sound cards at the time couldn't make a very real sound). However, 10 years later, as the former predicted, multimedia PCs are the standard today, and everyone can use their PC to listen to CDs, play audio games, talk through Internet phones such as mobile phones, and almost everything. When PC audio is related, there will be a colorful multimedia world [3].
Just when people were skeptical about PC audio, the first "true" sound card came along, the famous Sound blaster 16, named 16 because of its 16-bit polyphony (yes Refers to the number of instruments that can be simulated simultaneously by the sound card when playing back MIDI), the sound card can perfectly synthesize audio effects, which is of epoch-making significance. We can finally remove the annoying PC speakers [3].
The second major change is the Sound blaster 64 Gold. This is the first sound card that makes people amazing. The SB 64 Gold using the EMU8000 audio is surprising in terms of its price and performance. The sound card can also be sold so expensive. ah? The sound from the sound card can also be so beautiful! Emu8000 supports 64-bit polyphony for the first time (32 are implemented by hardware, and the other 32 are generated by software developed by Creative), gold-plated terminals, 120db dynamic range, 96db signal-to-noise ratio, I believe the sound quality is better than some at that time. The domestic CD player is even better! Everything is custom made for the highest quality acoustics. Of course, the shortcomings of this sound card are still obvious. First, the ISA bus is used, which limits the performance of the PC audio system and can only realize virtual 3D audio technology. Moreover, during playback, due to the use of the low-bandwidth ISA bus, the There are still some problems with signal-to-noise ratio and fidelity; the other is that onboard "sound memory" (memory used to store the sound library) must be used, and the memory of these sound cards is very expensive (in fact, it is not ordinary DRAM. Well), it originally only brought 4MB. In order to obtain better synthesis effects, many professional MIDI producers still pay for more sound storage to store a sound library with better effects. Through this combination, the Sound blaster 64 Gold can play back very pleasant synthetic music, which once excited many computer MIDI enthusiasts