Protocols - PatternAgents/Electronics_One_Workshop GitHub Wiki

MIDI

MIDI (Musical Instrument Digital Interface) is a technical standard that describes a protocol, digital interface and connectors and allows a wide variety of electronic musical instruments, computers and other related devices to connect and communicate with one another. A single MIDI link can carry up to sixteen channels of information, each of which can be routed to a separate device.
MIDI carries event messages that specify notation, pitch and velocity, control signals for parameters such as volume, vibrato, audio panning, cues, and clock signals that set and synchronize tempo between multiple devices. These messages are sent via a MIDI cable to other devices where they control sound generation and other features. This data can also be recorded into a hardware or software device called a sequencer, which can be used to edit the data and to play it back at a later time.
MIDI technology was standardized in 1983 by a panel of music industry representatives, and is maintained by the MIDI Manufacturers Association (MMA). All official MIDI standards are jointly developed and published by the MMA in Los Angeles, California, US, and for Japan, the MIDI Committee of the Association of Musical Electronics Industry (AMEI) in Tokyo.
We'll cover MIDI because it is the basis for Firmata, a method to remotely control small microprocessor systems.

Firmata is a protocol for communicating with microcontrollers from software on a computer (or smartphone/tablet, etc). The protocol can be implemented in firmware on any microcontroller architecture as well as software on any computer software package (see list of client libraries below).
Firmata is based on the midi message format in that commands bytes are 8 bits and data bytes are 7 bits. For example the midi Channel Pressure (Command: 0xD0) message is 2 bytes long, in Firmata the Command 0xD0 is used to enable reporting for a digital port (collection of 8 pins). Both the midi and Firmata versions are 2 bytes long, but the meaning is obviously different. In Firmata, the number of bytes in a message must conform with the corresponding midi message. Midi System Exclusive (Sysex) messages however, can be any length and are therefore used most prominently throughout the Firmata protocol.

Modbus is a serial communications protocol originally published by Modicon (now Schneider Electric) in 1979 for use with its programmable logic controllers (PLCs). Simple and robust, it has since become a de facto standard communication protocol, and it is now a commonly available means of connecting industrial electronic devices.

The main reasons for the use of Modbus in the industrial environment are:
- developed with industrial applications in mind
- openly published and royalty-free
- easy to deploy and maintain
- moves raw bits or words without placing many restrictions on vendors
Modbus enables communication among many devices connected to the same network, for example a system that measures temperature and humidity and communicates the results to a computer. Modbus is often used to connect a supervisory computer with a remote terminal unit (RTU) in supervisory control and data acquisition (SCADA) systems. Many of the data types are named from its use in driving relays: a single-bit physical output is called a coil, and a single-bit physical input is called a discrete input or a contact.

Embedis by PatternAgents is an open source library for creating simple embedded dictionary servers.
Embedis is used for embedding key-value dictionaries into the SRAM, FLASH, FRAM, NVSRAM, EEPROM, or SDcard memory systems of small, limited resource, embedded computing platforms, such as the Arduino(AVR), Teensy(Cortex-M4), ESP8266, and others.
Embedis uses a serialization protocol compatile with the Redis data structure storage server.