Based on the ARM of medical data acquisition system for human-machine interface design (1)

0 introduction

Medical data acquisition system to provide timely and effective medical personnel to provide patients with first-hand data, help to strengthen the Hospital of modern information management and improve efficiency.

And in family health, it is able to meet people in a fast paced work life in timely and accurate informed of their own and their family's health. In equipment for daily use, good human-computer interface design, and will provide equipment use staff save considerable time and provides great convenience. This article mainly to LM3S3748 as the core, and TFT LCD display devices as a system, but with a touch screen and handles controller as the system control device, describes the design of human-machine interface.

1 system hardware design

The system consists primarily of human-computer interface for TFT LCD, touch screen and handles controller, its structure diagram shown in Figure 1.

With TFT LCD brightness, contrast, layered strong, colourful, therefore, does not take into account the electricity consumption, TFT LCD is a good choice. Touch-screen used to ADC chip ADS7843 touch panel data sampling, the sampling of output values after calibration program that can receive its physical coordinates of the touch screen. Handle the controller using Modbus Protocol, and via the serial port on the core Board control.

1.1 control unit

This system of control unit may use TI company LM3S3748, supports up to 50 MHz ARM Codex-M3 kernel and 128 KByte FIASH, 64 KByte SRAM.

At the same time, integrated with USB HOST/DEVICE/OTG, sleep module, quadrature encoder, ADC, with dead by deleting, temperature sensor, analog comparators, UART, SSI, general-purpose timer, I2C, CCP, DMA controller, and other peripherals. In addition, the chip also has a library, driver curing can better meet the system requirements.

1.2 LCD interface circuit

LCD can choose 3.2 inch TFT (240 x 320) color LCD with touch 26 million module that supports SD cards and DATAFLASH, supports both 16-bit/8 bit mode.

The module can display arbitrary rotation of 180 degrees, and with a touch screen and touch controller chip. Module 16-bit parallel interface default i8080 and optional 8-bit parallel interface. Its LCD interface circuit shown in Figure 2.

1.3 touchscreen control circuit

Touch screen control chip used in the production company is TI ADS7843 4 wire resistive touch screen interface chips.

It is a synchronous serial interface with 12-bit sampling ADC. ADS7843 has two auxiliary input (IN3, IN4), can be set to 8-bit or 12-bit mode.

ADS7843 touch screen can be connected to X + will touch signal input to the A/D converter, open at the Y-Y + and drive, and then digital voltage, X + to get the current y position of the measurement results, for the same reason, you can get the X-coordinate of the logical coordinates.

When you get the X, Y coordinates of the logical, through SPI interface to feed data to data processing by LM3S3748. Its external circuit ADS7843 as shown in Figure 3.

1.4 RS232 serial communication circuit

RS232 serial port is used primarily to handle the controller and the core board communications, this is similar to the human-machine interface keyboard interface.

They communicate via Modbus Protocol. The RS232 serial port communication circuit shown in Figure 4.

2 system software design

2.1 touchscreen software design