Connection between max1169adc and PIC Microcontrol

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Max1169 ADC and PIC microcontroller interface

Abstract: this application note describes how to connect max1169 analog-to-digital converter (ADC) to PIC microcontroller. The example circuit and software of 8f442 corresponding to pic1 that this measurement will be fruitless are provided. The software includes function calls to connect ADC to PIC microcontroller at 400kHz using internal MSSP I C port

max1169 is a 16 bit, low-power ADC with I C compatible 2-wire serial interface. The interface of max1169 can support fast mode (400kHz) and high-speed mode (up to 1.7MHz)

this application note includes example application circuits and software for pic18f442. The software provides function calls to connect ADC to PIC microcontroller at 400kHz using internal MSSP I C port. Because other microcontrollers have similar on-chip peripherals, the I C communication program provided in the example is intentionally split into separate I c function calls for rapid migration to other microcontrollers. Table 1 shows the separate I C interface function calls used in the assembler example

the application circuit discussed here adopts max1169evkit, including max1169, input buffer (max4430) and verified PCB. Pic and RS-232 transceiver IC (MAX3232) are not installed on max1169evkit board. But it has been added to the system. Figure 1 shows a complete application circuit. The SCL and SDA pads on max1169evkit facilitate the connection of I C compatible serial interfaces. During 400kHz I C communication, connect 1.5k pull-up resistor on R3 and R4

the pin arrangement of max1169 facilitates the isolation of analog part and digital part. The analog part is gathered on the pin and distributed on the right side of the IC; The digital part is gathered in the pin and distributed on the left side of the IC. Pin 14 also belongs to the digital part, but it can be easily organized with the left side of the IC. For best performance, separate analog and digital power supplies are recommended, as shown in the schematic diagram in Figure 1

Figure 1 Max1169 application schematic diagram

separates the analog ground from the speed control of the moving beam of the experimental machine (as shown in Figure 2), which can get a better practical effect. Using ferrite beads, such as TDK mmz1608b601c, connect two ground planes. This layout can avoid the clock and its harmonic components of the microcontroller system being fed into the analog ground. It is known that the system clock of pic18f442 is 40MHz. Considering the special impedance and frequency characteristics of mmz1608b601c, we chose this ferrite bead which can not find out the cause of fatigue failure. Figure 3 shows the variation curve of mmz1608b601c resistance with frequency for different models and designs of various materials

Figure 2 Separate analog ground and digital ground

Figure 3 TDK mmz1608b601c ferrite bead impedance versus frequency curve

the assembler in the example reads the continuous conversion results of 16 bit ADC max1169 at 400kHz through PIC's 2-wire interface. Once the pic receives the data (digitized analog voltage), it will immediately send it out at the rate of 115kbps through the software UART. RS-232 transceiver sends data to personal computer with standard serial interface

table 1 Single I C interface function call

hwi C_ W_ slaveAddr

Performs all I C compatible write operations including the initial slave address write frame.

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