SPI interface and microcontroller interface principle circuit diagram

The SPI interface is a synchronous serial data transmission between the CPU and peripheral low-speed devices. Under the shift pulse of the master device, the data is transmitted bit by bit, with the high bit in front and the low bit in the back. It is full-duplex communication and the overall data transmission speed is It is faster than the I2C bus, and the speed can reach several Mbps.

For a 250μΩ shunt, the voltage signal at both ends is 250×40=10,000μV at 40A, which is 10mVRMS. The sampling signal is very small, so the channel gain should be set to the maximum, which is 32 times. At this time, the maximum signal input amplitude is 26.25mVRMS. .The actual maximum input signal is smaller than the allowed maximum input signal, and the shunt resistance value should be selected appropriately.

As the SPI bus master, LPC9401 outputs a clock signal, and STPM01 communicates according to the clock signal of SCLNLC. The following is a schematic diagram of the SPI interface and microcontroller interface provided by Shenzhen Jieduobang PCB Circuit Board Company.