According to the principle of fluorescence immunoassay, the immunofluorescence detector guides clinical drug by rapidly quantitatively detecting CRP (full C-reactive protein) to determine the nature of antigen or antibody. The detection process is shown in Figure 1.

Immunofluorescence detector control panel function requirements:

l Chinese and English display interface and touch screen operation;

l RS-232 interface, used to drive micro-play, communicate with the microcontroller;

l Ethernet interface, connected to LIS (Laboratory Information Management System);

l Support floating point arithmetic, fast data processing;

l Reliable electromagnetic compatibility design, medical device certification.

1.1 Immunofluorescence detector control board design difficulties

1. Medical device certification failed, sales were blocked

Medical testing equipment is intelligent electronic equipment. Static electricity and electromagnetic interference directly affect the sensitivity of detection and the accuracy of detection results, causing doctors to misjudge and indirectly affect the patient's personal safety. Therefore, medical devices must pass strict electromagnetic compatibility tests before they are put on the market. At the beginning of the design of the control panel, the engineer simply understood that the shielding and good grounding could pass the electromagnetic compatibility design, and in the product certification test, the most basic electrostatic contact discharge 4KV could not pass.

2. The touch screen "flying point" is serious, frequent operation errors

The detector adopts a 5.6-inch four-wire resistive touch screen. During the operation, the “flying point” phenomenon is serious, resulting in frequent misoperations and affecting the user experience. Through the touch screen to draw lines, you can find obvious "burrs" and "waves", as shown in Figure 2.

3. The sporadic power failure restart failed, causing the device to not work properly.

The fluorescence detector was shut down to take a direct power-off mode. During the test, it was found that in the frequent operation of the switch, the device occasionally failed to start. The analysis found that the operating system file system was lost after power-off (originally stored in flash). ). The sporadic phenomenon reappeared to varying degrees in all early test prototypes, seriously affecting product quality.

1.2 Program recommendation

In response to customer's functional requirements and design difficulties, ZLG Zhiyuan Electronics recommended the M3352 industrial control core board to assist customers in rapid product development. The project block diagram is shown in Figure 3.

1. Electromagnetic compatibility anti-jamming design

Electromagnetic compatibility anti-jamming design includes grounding, shielding, filtering, interface circuit protection, PCB layout design, etc. The M3352 core board is equipped with an open source evaluation board that passes the electromagnetic compatibility industry level 4 test. Such as air discharge ± 15KV test, contact discharge ± 8KV test, lightning strike (surge) immunity 2KV capacitive coupling and gas discharge tube coupling (1 time / minute) test.

2. Touch screen hardware filtering combined with software driver to remove "flying point"

The four-wire resistive touch screen interface circuit is shown in Figure 4. In order to prevent the touch screen from being disturbed, a large recognition error occurs, and a low-pass filter circuit is added; attention should be paid to the selection of capacitors C78-C81, and the capacitance cannot exceed 0.01 μF, otherwise the touch screen reflects It is slow or unable to identify properly. It is recommended to take 1nF.

In addition to hardware filtering, the touch screen driver needs to increase the algorithm for removing the "flying point". The final touch screen effect is shown in Figure 5. The drawing line is very smooth.

3. 100,000 flash power failure test, reliable file system

The device cannot be started after the device is powered off and restarted. Most of the files are damaged or the file system is lost due to unexpected power failure. A file system is a method and data structure used by an operating system to clarify files on a disk or partition, that is, a method of organizing files on a disk.

File system common exceptions:

l The file system loses power, the system fails to start, and important record data is lost.

l The file system is damaged, the storage data is out of order, and important files cannot be opened for reading.

M3352 core board and ZLG Zhiyuan electronic ARM industrial control products, the file system has passed 100,000 frequent power-on and power-off tests during the reading and writing process:

l Ensure that the file system is reliable;

l Make sure that the accidental power failure file system is not lost.

1.3 Recommended Products

M3352 core board, static, surge, pulse anti-jamming design meets industry level 4;

Main features:

l TI Cortex-A8 AM3352 processor, 800MHz frequency

l Support WinCE and embedded Linux operating system

l 6-way UART interface

l 2-way CAN interface

l 2-way high-speed USB OTG (built-in PHY, 480Mbps)

l 2-way Ethernet (1 of which is Gigabit MAC)

l Mechanical size 60mmx45mm

l Working temperature -40 ° C ~ +85 ° C

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