I. Introduction to BLE MIDI
1.1 ? Apple in 2014 to the design of low-power Bluetooth (BLE)-enabled MIDI protocol, and then MMA members in June 2015 to the protocol as an industry standard. This resulted in the BLE MIDI protocol. Simply put, it is the MIDI protocol that supports BLE.
1.2 The principle of the software is to take the BLE MIDI data transmitted from Bluetooth, parse it into the traditional standard MIDI data, and then output it through the serial port, and by the same token, the midi data from the serial port can be encoded as BLE MIDI data to be sent to the mobile terminal.
Classification of Bluetooth MIDI transmission
1.3 Schematic diagram of signal transmission
1.4 Comparison of BLE MIDI and traditional methods Description
Species Description Review
1. Wired transmission is a coaxial audio cable that connects an instrument to the speaker on the line more troublesome, and the layout of the scene is difficult to see when there is more than one instrument, but the sound quality is very good. Transmission loss is small, support multiple instruments at the same time access to a speaker, generally less
2, 2.4G transmission with a pair of 2.4G module through the wireless reception and transmission of audio transmission to the speaker price is expensive, a pair of modules to 30 dollars or so, the transmission loss is relatively small, to support multiple musical instruments at the same time to a speaker, generally less
3, Bluetooth transmitter transmission musical instrument A side made of Bluetooth transmitter mode, and Bluetooth speakers through Bluetooth technology transmission (Bluetooth speakers work in receive mode) cheap, a chip less than 5 yuan, transmission loss is acceptable, with no problem in general products, can only support a one-to-one supporting the use of more
[if !supportLists]4, [endif]Bluetooth MIDI
Chip KT2025
Through the Bluetooth BLE transmitting mode, the instrument's audio transmission to the phone, the phone and then the data through Bluetooth transmission to the Bluetooth speaker. At present, only the iPhone supports MIDI protocol cheap, a chip less than 5 yuan, with the data transmission, loss is relatively small, the lead sound quality is mainly the chip's sampling class, support for multiple musical instruments at the same time transmitted to the phone, the future mainstream development mode
Second, the BLE MIDI chip
2.1, the chip
Introduction The KT2025 chip is a 4-in-1 single chip that supports Bluetooth as well as USB flash drive and TF card playback. The highlights of the chip are the support for lossless music playback and the simple and clear serial port control function, support for BLE pass-through, BLE MIDI, and SPP pass-through function. It also supports BLE transmitting, BLE MIDI, and SPP transmitting functions. This greatly reduces the difficulty of embedding Bluetooth in other products.
2.2 Chip parameters
Name parameters
MP3 file format 1, support for all bit rate 11172-3 and ISO13813-3 layer3 audio decoding
2, the sample rate support (KHZ): 8/11.025/12/16/22.05/24/32/44.1/48, the sampling rate is not the same as the sampling rate.
3, support for Normal, Jazz, Classic, Pop, Rock and other sound effects
4, support for 24-bit DAC
USB interface 2.0 standard
UART interface standard serial port, TTL level, baud rate can be set to connect to the PC level conversion is required [eg: CH340G - USB TTL]
Input voltage 3.3V-5V [7805 rear string of a diode for the best]
Rated current 20MA [static]
Low-power current <200uA
Chip DAC drive the main chip DAC can only be driven by the headset
Operating temperature [-40 degrees] -- [80 degrees].
Humidity 5% ~ 95%
Chip Model KT2025 SSOP24
2.3 ? Chip features
1, the chip uses the SSOP24 narrow body package
2, the chip has fewer peripheral components, only 6 capacitors, 5 105, 1 2P7, plus a 24M crystal on it
3, the chip has a high degree of integration, powerful, support for the traditional bluetooth MP3 function, built-in FM radio function
4, Bluetooth audio chip program
5, Bluetooth digital transmission program - BLE
6, Bluetooth digital transmission program, dual-mode BLE and SPP
7, Bluetooth audio + dual-mode data
8, support for Bluetooth BLE MIDI
9, support for generic AT serial commands
2.4 Standard Schematic
Third, the terminology descriptionFunction Remarks
Public **** function refers to all modes will have the function, such as adjusting the volume, mute, switch modes, reset and other operations
Music, MUSIC, device refers to the plug-in TF, plug in the USB flash drive playback function
Bluetooth Mode we have here in the bluetooth both support for audio, but also at the same time support for BLE and SPP digital transmission
BLE is a standard protocol for Bluetooth communication, and Bluetooth audio is independent of each other
SPP is also a link in the Bluetooth communication protocol, and Bluetooth audio is together
Transmission refers to what the cell phone sends to the Bluetooth, the Bluetooth will be sent out through the serial port, the same as the other way around
Serial port refers to the external interface of Bluetooth chip, that is, UEFI. [endif] Chip application scenarios
1, Bluetooth audio products such as: Bluetooth speakers, Bluetooth headset, car Bluetooth, etc.
2, Bluetooth digital transmission products such as: smart door locks, car OBD detection, smart cars, printers, medical equipment, data collection?BLE MID
3, Bluetooth digital transmission + audio products such as: Bluetooth music lights, Bluetooth radio
Notes
Note: Requirements for ultra-low power consumption, the choice of this program is not appropriate
V. Summary
The more we move forward, Bluetooth is used in musical instruments is a trend, we will also be more advantageous in this field.