1, Comparison of Technical Characteristics: Balancing Speed and Complexity
SPI interface: a "single threaded expert" for high-speed transmission
SPI adopts a four wire architecture (SCLK, MOSI, MISO, CS) to achieve synchronous data transmission through full duplex communication. Its core advantages lie in:
Transmission speed: The theoretical speed can reach tens of Mbps, far exceeding the 1Mbps upper limit of I2C. Taking Yangrun Electronics' SPI interface segment code screen as an example, its driver chip supports a maximum clock frequency of 10MHz, which can meet the real-time data display requirements of medical equipment.
Multi slave support: Multiple slave devices can be expanded through independent chip selection signals (CS). ADI's ADGS1412 switch chip adopts daisy chain mode, requiring only 4 GPIO to control 8 four channel switches, significantly reducing PCB space occupation.
Timing flexibility: Supports the combination of CPOL/CPHA four modes, which can adapt to the timing requirements of different manufacturers. For example, a certain automotive instrument project achieves stable communication with MCU through SPI mode 1 (CPOL=0, CPHA=1).
However, SPI has a high hardware complexity, and the four wire architecture requires attention to signal integrity during PCB wiring, especially in high-frequency scenarios where it is susceptible to electromagnetic interference.
I2C interface: the "bus master" of minimalist design
I2C only requires two wires (SDA, SCL) to achieve multi master and multi slave communication, and its technical highlights include:
Hardware simplicity: Bus sharing is achieved through pull-up resistors. A certain smart meter project uses an I2C interface LCD1602 module, which only requires 2 GPIO to drive the display, saving MCU resources by up to 75%.
Address configurable: The device address can be configured through hardware jumpers or software, and supports mounting multiple display modules on the same bus. The VKL060 driver chip supports variable addresses ranging from 0x20 to 0x27, making it convenient for system expansion.
Low power consumption characteristics: The working current only needs microampere level. After a certain medical monitor adopts I2C segment code screen, the standby power consumption of the whole machine is reduced by 40%, which meets the IEC 60601 medical safety standard.
However, the transmission rate of I2C is limited by bus capacitance, with standard mode only 100kbps and fast mode up to 400kbps, which limits its performance in scenarios that require high-speed refresh, such as dynamic chart displays.
2, Application scenario decision tree: precise matching from requirements to interfaces
High speed refresh requirement: For example, the tachometer on the car dashboard needs to be updated at least 50 times per second for real-time display.
Strong electromagnetic interference environment: The noise generated by the frequency converter inside the industrial control cabinet may interfere with the I2C bus, while SPI's differential signal transmission is more resistant to interference.
Multi device expansion requirements: A certain testing instrument project requires simultaneous control of 8 segment code screens. Using SPI daisy chain mode, only 7 GPIO are needed, saving 50% of pin resources compared to I2C scheme.
Low cost MCU solution: When the MCU lacks a hardware I2C controller, SPI can be implemented through software simulation, and the software implementation complexity of I2C is significantly higher.
Long distance transmission: SPI signal lines can be extended to over 10 meters through differential conversion chips to meet the distributed display needs of large equipment.
Prioritize the five major scenarios of I2C
Ultra low power consumption system: Portable devices powered by batteries (such as handheld infrared thermometers) need to control the display power consumption to milliwatts.
Space limited design: The internal PCB area of smart wearable devices is only a few square centimeters, and the two-wire architecture of I2C can save valuable space.
Multi sensor collaboration: When the system needs to simultaneously connect I2C devices such as temperature sensors and accelerometers, sharing a bus can simplify the design. A smart home control screen project integrates segment code screens, ambient light sensors, and touch chips through I2C bus, reducing BOM costs by 30%.
Hot plug requirements: The I2C bus supports online device plugging and is suitable for industrial HMI systems that require dynamic configuration.
Standardized protocol compatibility: When the system needs to comply with derivative protocols such as SMBus and PMBus, I2C is the only option.
3, Industry Practice: Technology Route Selection of Top Manufacturers
Yangrun Electronics: "Dual track Strategy" of SPI and I2C
As a leading enterprise in the industrial display field by 2025, Yangrun Electronics adopts a modular architecture in the design of segment code screen interfaces
Standard product: Provides SPI/I2C dual interface options to meet different customer needs through jumper switching. Its latest HY-LCD6402 module integrates both SPI and I2C controllers, allowing users to dynamically choose according to their actual scenarios.
Customized solution: Develop a gateway module that supports CAN bus to SPI conversion for the automotive electronics field, achieving seamless integration between the onboard ECU and the segment code screen; In the field of medical equipment, a bridge chip for I2C to parallel interface conversion has been launched to solve the compatibility problem between traditional parallel segment code screens and modern low-power MCUs.
Multiplexing scheme: ADG1607 four channel switch can expand a single SPI host to four slave devices, saving 75% GPIO resources compared to traditional schemes.
Chrysanthemum chain optimization: In a certain photovoltaic inverter project, cascade control of 16 segment code screens was achieved through ADGS1412, and signal integrity was maintained even when the bus length reached 5 meters.
Yongjia Microelectronics: The Ultimate Pursuit of I2C Low Power Consumption
The VKL060 driver chip achieves microampere level power consumption through the following technologies:
Dynamic bias adjustment: Automatically adjust the COM/SEG driving voltage according to the display content, with a power consumption of only 0.5 μ A during static display.
Intelligent sleep mode: When no data updates are detected, it automatically enters a deep sleep state with a wake-up time of less than 100 μ s.
Built in oscillator: eliminates the need for external crystal oscillators, further reducing system power consumption.
