The mixed-signal oscilloscope made its debut in 1993 and initially came equipped with two analog channels alongside either eight or sixteen digital channels. Over the years, the mainstay of the MSO became an indispensable tool for embedded system designers. Typically, these instruments were configured with either two or four analog channels paired with sixteen digital channels. Engineers preferred MSOs because they could monitor two to four signals simultaneously while scaling up to twenty signals without needing to rely solely on a logic analyzer.
While this configuration has been widely accepted for quite some time, one must wonder if it still meets the demands of today's embedded systems. This is a pressing question for both oscilloscope manufacturers and engineers working in embedded systems. Manufacturers need to ensure their products offer functionalities that customers truly value and are willing to pay for, while engineers seek tools tailored to their specific tasks.
This realization has spurred several research initiatives worldwide, with embedded system engineers delving deeper into the optimal number of oscilloscope channels. The latest 5 series of MSOs reflects these investigations in various aspects, expanding the number of analog channels to six or eight and offering between eight to sixty-four digital channels. Additionally, the digital channels can now be reconfigured during operation.
Despite the success of four-channel MSOs in recent years, it’s clear that the conventional mix of analog and digital channels often suffices for most embedded designs. Engineers typically manage with four channels, yet a significant portion (35% of our survey) stated they would ideally need eight analog channels.
In the past, when engineers required more than four analog inputs, they often used two oscilloscopes simultaneously—a process known as "cascading." This approach presented numerous challenges. Synchronizing multiple oscilloscopes for simultaneous acquisitions required careful trigger settings and precise cable connections. Comparing data across two separate displays was cumbersome, and many engineers had to manually transfer the data to a computer for further analysis. Even if the oscilloscopes were identical models, achieving synchronization took considerable time, and using different models exacerbated the problem.
When it comes to digital channels, reducing the number is just as significant as increasing them. Many engineers expressed frustration over being compelled to purchase 16 digital channels when they only needed eight. Our study revealed that about 75% of respondents didn’t want 16 digital channels—some desired fewer, others more.
For embedded system designers, flexibility is paramount. Our research showed that 79% of embedded engineers prioritize oscilloscopes that cater to future needs and provide multifunctional capabilities to address the demands of design teams under immense pressure.
The most frequent response when discussing which stages require additional channels and flexibility during system-level debugging involved subsystems merging together. As multiple processors, power supplies, serial buses, and I/O devices integrate, the ability to view the entire system becomes crucial. Traditionally, engineers use two or four channels to capture data repeatedly, tracing signal paths to identify root causes. However, modern systems often handle multiple sensors, actuators, and communication buses, making traditional debugging methods challenging.
Another pain point for engineers lies in the growing complexity of power supplies in contemporary systems. To optimize power consumption, performance, and speed, even simpler systems may feature a 12V main supply along with multiple 5V, 3.3V, and 1.8V supplies. Verifying and commissioning these power-on and power-off sequences, especially concerning other control signals or status lines, demands more channels and testing.
Some innovative engineers reported using variable thresholds on digital MSO channels to check power sequences. By setting the digital channel threshold slightly below the nominal voltage, they created a "timing diagram" showing power supply, reset lines, interrupts, status lines, etc. While this method works, it ignores the analog characteristics of the signal. Most engineers prefer using analog channels for such tests.
For many applications, a standard setup of four analog channels and sixteen digital channels suffices. However, encountering new challenges is inevitable, and it’s beneficial to have alternative configurations available.
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