Introduction to common internal buses

1. IIC

The IIC (Inter-Integrated Circuit) bus is a two-wire serial bus developed by PHILIPS, which is used to connect the microcontroller and its peripheral devices. The I2C bus uses two wires (SDA and SCL) to transfer information between the bus and devices, serial communication between a microcontroller and an external device, or bidirectional data transfer between a master device and a slave device. I2C is output by OD, and most I2Cs are 2-wire (clock and data), which are generally used to transmit control signals.

2. IIS

I2S (Inter-IC Sound Bus) is a bus standard developed by Philips for audio data transmission between digital audio devices. I2S has 3 main signals: 1. Serial clock SCLK, also called bit clock, that is, corresponding to each bit of digital audio data, SCLK has 1 pulse. 2. The frame clock LRCK is used to switch the data of the left and right channels. When LRCK is "1", it means that the data of the left channel is being transmitted, and when it is "0", it means that the data of the right channel is being transmitted. 3. Serial data SDATA is the audio data represented by two's complement. Sometimes in order to enable better synchronization between systems, another signal MCLK needs to be transmitted, called the master clock, also called the system clock (Sys Clock).

3. SPI

SPI (Serial Peripheral Interface: Serial Peripheral Interface); SPI was first defined by Motorola on its MC68HCXX series processors. The SPI interface is mainly used between EEPROM, FLASH, real-time clock, AD converter, digital signal processor and digital signal decoder. The SPI interface works in a master-slave mode. This mode usually has a master device and one or more slave devices. Its interface includes the following four signals: (1) MOSI – data output from the master device, data input from the slave device (2) ) MISO - master device data input, slave device data output (3) SCLK - clock signal, generated by the master device (4) /SS - slave device enable signal, controlled by the master device.

4. UART

UART (Universal Asynchronous Receiver Transmitter: Universal Asynchronous Receiver). Convert the parallel data transmitted from the computer to the output serial data stream. Converts serial data from outside the computer into bytes for use by devices that use parallel data inside the computer. Add parity bits to the output serial data stream, and perform parity check on the data stream received from outside. Add start-stop markers to the output data stream and remove start-stop markers from the receive data stream. Handles interrupts signaled by the keyboard or mouse (keyboards and mice are also serial devices). It can handle the synchronization management of the computer and external serial devices. Some high-end UARTs also provide buffers for input and output data. Commonly used TXD, RXD, /RTS, /CTS.

5. JTAG

JTAG (Joint Test Action Group) is an international standard test protocol (IEEE1149.1 compliant), mainly used for chip internal testing. The standard JTAG interface is 4 lines: TMS, TCK, TDI, TDO, which are mode selection, clock, data input and data output lines respectively. The test reset signal (TRST, generally active low) is generally used as an optional fifth port signal. A CPU with a JTAGDebug interface module, as long as the clock is normal, can access the internal registers of the CPU and devices hung on the CPU bus through the JTAG interface, such as FLASH, RAM, registers of the built-in module, such as UART, Timers, GPIO, etc. register.

6. CAN

The full name of CAN is "Controller Area Network", that is, the controller area network, which is one of the most widely used field buses in the world. Initially, CAN was designed as a microcontroller communication in the automotive environment, exchanging information between the ECUs of the electronic control devices in the vehicle to form an automotive electronic control network. For example, the CAN control device is embedded in the engine management system, transmission controller, instrumentation equipment, and electronic backbone system. In a single network composed of CAN bus, in theory, an infinite number of nodes can be connected. In practical applications, the number of nodes is limited by the electrical characteristics of the network hardware. For example, when using a Philips P82C250 as a CAN transceiver, 110 nodes are allowed in the same network. CAN provides data transfer rates up to 1Mbit/s, which makes real-time control very easy. In addition, the error detection feature of the hardware also enhances the anti-electromagnetic interference capability of CAN.

7. SDIO

SDIO is an SD-type expansion interface. In addition to SD cards, it can also be connected to devices that support SDIO interfaces. The purpose of the socket is not only to insert memory cards. PDAs, laptops, etc. that support SDIO interface can be connected to GPS receivers, Wi-Fi or Bluetooth adapters, modems, LAN adapters, barcode readers, FM radios, TV receivers, RF authentication readers, Or digital cameras and other devices that use SD standard interfaces.

8. GPIO

GPIO (General Purpose Input Output) or bus expanders simplify I/O expansion using industry standard I2C, SMBus? or SPI? interfaces. GPIO products can provide additional control and monitoring functions when the microcontroller or chipset does not have enough I/O ports, or when the system requires remote serial communication or control.

Each GPIO port can be individually configured as input or output through software.