AI3281 AI3281-A-V001 has an internal reference voltage, both pin 4# (REF) is 4.096V, so the full range of the A/D conversion is 4.096V. and the input signal is 0~5V, so it is necessary to add a stage of op-amps to convert 0~5V to 0~4.096V and then feed it to the MAX187. P1.3 of the AT89C52 is connected to the chip select terminal (CS) of the MAX187, and P1.4 of the AT89C52 is connected to the serial clock signal terminal (SCLK) of the MAX187. P1.3 of AT89C52 is connected to the chip select terminal (CS) of MAX187, P1.4 of AT89C52 is connected to the serial clock signal terminal (SCLK) of MAX187, and P1.5 of AT89C52 is connected to the serial data output terminal (DOUT) of MAX187. The analogue sampled values are stored in the memory of the microcontroller and then transmitted to the PLC through the serial port of the microcontroller.

AI3281 AI3281-A-V001 uses a 12-bit D/A converter chip MAX531 to implement the digital-to-touch conversion. We connect an operational amplifier to the output of MAX531 to adjust the analogue output to 0-5V, and the hardware circuit of the output part is shown in Figure 3. Here, MAX531 is a 12-bit serial D / A, with high conversion speed, MAX531 has an internal reference voltage, both 10 # pin (REFOUT) for 2.048V, so the full range of D / A conversion for 2.048V.

AI3281 AI3281-A-V001 output signal is generally required to be a standard 0 ~ 5V, therefore, to add a level of op-amp MAX531 output 0 ~ 2.048V signal into a 0 ~ 5V signal. AT89C52 P1.0 and the MAX531 serial clock signal terminal (SCLK) is connected to AT89C52 P1.1 and the MAX531 serial data signal terminal (SCLK) connected to AT89C52 P1.1 and the MAX531 serial data signal signal terminal (SCLK) is connected to AT89C52 P1.1 and the MAX531 serial data signal signal terminal (SCLK). P1.0 of AT89C52 is connected to the serial clock signal terminal (SCLK) of MAX531, P1.1 of AT89C52 is connected to the serial data input terminal (DIN) of MAX531, and P1.2 of AT89C52 is connected to the chip selector terminal (CS) of MAX531. The PLC transmits analogue quantities to be output to the MCU through the serial port, and then deposits them into the memory, which is then converted into D/A and outputted by the MCU.