CMOS Drake Depends on Blackfin® for Heart Defibrillator
It should come as no surprise that the same Brazilian passion that brought us the syncopated but steady beat of the Bossa Nova should produce a signal-processing solution that can kick a rhythmically failed human heart back into step. With more than 12 years of experience in the medical market, CMOS Drake, located in Santa Efigenia, Belo Horizonte, MG Brazil, makes a line of automatic external defibrillators (AEDs) designed to treat patients with life-threatening heart rhythms, and it is the only company in Brazil to do so.
When this medical manufacturer was looking to shift to a new level of technology from what it was using previously, it chose a Blackfin® ADSP-BF533 processor from Analog Devices, Inc. (ADI) for the job. Eduardo Azevedo, a biomedical development engineer at CMOS Drake, said, "With Blackfin, we were able to achieve top-level product specifications with a competitive price for the Brazilian market."
Blackfin to the Rescue
CMOS Drake needed a high level of signal processing for its sophisticated electrocardiogram (ECG)-analysis algorithm, and that's one of several reasons the company decided to use Blackfin as its core processor. "Blackfin is performing some hard signal-processing tasks such as QRS detection, parameter extraction, FFT, filtering, and analysis of arrhythmias," said Azevedo. "We're using VisualDSP++ and the VisualDSP++ Kernel (VDK) as the only operating system. Our source code is quite large. We are actually working with six threads, which required extra effort in the design phase and a precise buffer structure in order to exchange data through all of the processes."
VisualDSP++ is an easy-to-use integrated software development and debugging environment (IDDE) that enables programmers to define and manage software development. The ADI VDK incorporates scheduling and resource management tailored for signal-processing applications. "Blackfin is also linked with an ADI audio CODEC and two SoCs - PSoC and Cypress. Even with the heavy workload, the history tool in VisualDSP++ shows that Blackfin can handle the work easily - the processor is idle more than 40 percent of the time!"
But that's not all. "Another reason we chose the Blackfin ADSP-BF533 processor is because it enables the integration of signal processing and microcontrollor functions in a single device," said Azevedo. Because of the combination, Blackfin was ideal for controlling processes such as the high-voltage unit that charges the storage capacitor and creates a biphasic output current that ultimately delivers a shock to the heart. "Blackfin also includes the digital multi-purpose pins we needed to control the muxes, or analog switches, that exist in the medical circuitry and serial communication hardware to integrate the functional blocks within our device," Azevedo continued. Blackfin's flag pins control the processes, described above, that enable the flow of the electrical current.
Sudden cardiac arrest, which is usually due to abnormal heart rhythms called arrhythmias, if left untreated, is a major cause of death. When this occurs, a portable AED device (administered by an emergency medical technician ((EMT)) or a paramedic) can deliver an electrical current to the heart and save a life. But it has to be done quickly when the heart stops, an electrical shock must be delivered within two to four minutes or the patient will die. As such, an AED is typically stored in a public place such as a corporate office, shopping mall, airport, sports stadium, school, or other venue where groups of people congregate, for easy access. Police, fire, and ambulance personnel are often trained on AED devices and have them on board, as they are first responders in crisis situations.
An AED is a very colorful portable battery-operated device that comprises a computer and a pair of pads (electrodes), and is used to defibrillate a heartbeat after sudden cardiac arrest. The device is designed to assist the user every step of the way. Once an operator places the electrodes on a person's chest, the AED analyzes the heart rhythm and instructs the operator in both words and text. If the device detects that the victim is indeed in cardiac arrest, it alerts the operator to deliver a shock. To do so, the AED controls a high-voltage unit that charges a storage capacitor and creates a biphasic output current. A biphasic output current is essentially a pattern of electrical flow where the current reverses direction in the middle of the waveform, flowing first from one electrode pad through the heart to the second electrode pad. It then moves back to the second pad through the heart and back to the first pad. The AED has a built-in safety mechanism in that it will not permit a shock to be given unless someone is, in fact, in cardiac arrest.
What's more, all of Blackfin's peripherals, except for the general-purpose I/O, real-time clock, and timers, are supported by a flexible direct memory architecture (DMA) structure. There is also a separate memory DMA channel dedicated to data transfers between the processor's various memory spaces, including external SDRAM and asynchronous memory. Multiple on-chip buses running at up to 133 MHz provide enough bandwidth to keep the processor core running along with activity on all of the on-chip and external peripherals. "Blackfin's data bus is wired to an LCD display, 32 MB of SDRAM, 2MB of flash memory and a compact flash memory that enable us to store code on and later exchange data with the outside world," said Azevedo. These features enable CMOS Drake to provide information to the AED operator via text messages and voice prompts - instructions that guide the operator through the process of defibrillating the victim's heart, or not, depending on the circumstances.
Fast Time to Market
With prices starting at $12.95 for quantities of 10,000 for Blackfin ADSP-BF533 processors running at 500 MHz, CMOS Drake found using Blackfin not only superb for its high-performance, but the processor is also excellent because it is so cost-effective. "When you consider that the overall cost of development with Blackfin is quite low, and then you add the affordable price of EzKit, and the fact that you can use Visual DSP++ free of charge initially [through the ADI Test Drive Program], that is quite a cost savings," said Azevedo. "Because of Blackfin, the final cost of our AED equipment has been significantly reduced."
VisualDSP++ and VDK allowed CMOS Drake to start the development process after a relatively short learning curve, according to Azevedo. "It took us about a year and a half from the time we decided to use Blackfin until the time the product was finished," he said. The company also used ADI's EzKit Lite Evaluation Kit, which comprises a standalone board and a suite of VisualDSP++ to facilitate architecture evaluations via a PC-hosted tool set so users can try out ADI's processors, or simulate, debug, and/or prototype applications. CMOS Drake also used the JTAG test access port to test and debug hardware and software.
With VisualDSP++, developers can use mixed C/C++ and assembly code (interleaved source and object information), as did CMOS Drake. Said Azevedo, "We used object-oriented programming in C++, which has proven successful for large-code systems, such as our AED, which has many satellite devices."
In the future, CMOS Drake plans to continue using ADI's Blackfin processors, preferably dual-core versions. In fact, the company also uses a full complement of ADI parts, including operational amplifiers, couplers, analog-to-digital converters (ADCs), multiplexers, and analog switches.
It's good to know that because of Blackfin, and some quick thinking on the part of dedicated individuals, a lot of healthy people can go on living without skipping a beat.
For more information about CMOS Drake, visit the company Web site at www.cmosdrake.com.br.
Read more Customer Case Studies like this...