1.1 background event
For the application of anesthetic in the patient's operation, when the anesthetic dose exceeds the standard, it is easy to cause the patient's heartbeat and respiratory arrest to cause brain damage. Traditional anesthetic injection relies on the experience of an anesthesiologist, while the new EEG monitoring TCI injection pump combines BIS (EEG monitoring) with TCI (Target Controlled Infusion) to truly achieve individualized sedation anesthesia in medical electronics, reducing Risk of anesthesia.
1.2 EEG monitoring TCI syringe pump control board function requirements
EEG monitoring TCI syringe pump on the basis of the conventional syringe pump, by receiving the data of "EEG analyzer" to analyze the decision-making injection volume and injection speed, making the injection more scientific and safer.
Control the main functional requirements of the motherboard :
Display interface, external 7-inch or more true color LCD, support touch screen;
RS-232 interface, connected to the EEG analyzer;
PWM, control injection motor;
ADC, collecting injection tube position data information;
Sound card, prompting of the injection process;
Ethernet, connect to the server, and achieve data upload;
1.3 EEG monitoring TCI syringe pump control board design difficulties
1. Touch screen "flying point", frequent operation errors
The syringe pump adopts a 7-inch four-wire resistive touch screen, which causes a "flying point" phenomenon during operation, resulting in frequent misoperations and affecting the user experience. Through the touch screen line, you can find obvious "burrs" and "waves", as shown in Figure 1.
Figure 1 touch screen operation line
2. The touch response is slow and occasionally crashes
EEG monitoring TCI syringe pump internal procedures are more complex, software processing tasks are more, when there is a touch button click, reflect too slow, and occasionally the system crashes, need to restart the device phenomenon.
3. The sporadic power failure restart failed, causing the device to fail to work properly.
The injection pump 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.
1.4 Our 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 2.
Figure 2 project block diagram
1. Touch screen hardware filtering combined with software driver to remove "flying point"
The four-wire resistive touch screen interface circuit is shown in Figure 3. In order to prevent the touch screen from being disturbed, a large recognition error occurs, and a low-pass filter circuit is added. It is necessary to pay attention to the selection of the capacitor 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.
Figure 3 touch screen circuit
In addition to hardware filtering, the touch screen driver needs to increase the algorithm to remove the "flying point". The final touch screen implementation effect is shown in Figure 4. The drawing line is very smooth.
Figure 4 touch screen line
2. Using industrial control core board, Cortex-A8 processor
Slow touch response and sporadic crashes are related to the complexity of the software processing and processor performance. At the same time, software design and hardware design issues (such as driver, power supply circuit, and motherboard anti-interference performance) are not excluded.
The M3352 core board uses the Cortex-A8 processor, with a frequency of up to 800Mhz, and the performance is more than 4 times that of the ordinary ARM9 processor, which fully meets the processor performance requirements of the syringe pump. At the same time, ZLG core board software and hardware have undergone rigorous stress testing, and the stability has been tested by various industries such as medical, electric power and military.
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:
The file system loses power, the system fails to start, and important record data is lost.
The file system is corrupted, 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 in the reading and writing process after 100,000 frequent power-on and test:
Ensure that the file system is reliable;
Make sure that the accidental power failure file system is not lost.
1.5 recommended products
Figure 6 M3352 core board
M3352 core board, static, surge, pulse anti-jamming design meets industry level 4;
Main features:
TI Cortex-A8 AM3352 processor, 800MHz clock speed
Support WinCE and embedded Linux operating system
6-way UART interface
2-way CAN interface
2-way high-speed USB OTG (built-in PHY, 480Mbps)
2-way Ethernet (1 of which is Gigabit MAC)
Mechanical size 60mmx45mm
Working temperature -40 ° C ~ +85 ° C
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