Developments in Mixed-Signal Oscilloscopes Accelerate Embedded Design Development

Abhishek A. Mutha is a senior technical correspondent at EFY

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Engineers, especially those working on embedded designs, bank on mixed-signal oscilloscopes (MSOs) right from the prototype stage to product testing. Embedded system designers debug their designs with analogue- and digital-channel capabilities in these oscilloscopes, which also provide a variety of triggering options. Let us take a look at the new capabilities added in these MSOs.

Faster, wider, higher, deeper: four buzzwords in MSOs
As embedded designs continue to grow speedily in numbers, manufacturers are continuously evolving their MSOs accordingly. With new applications emerging in the Internet of Things (IoT), wireless and various semiconductor technologies, MSOs are playing an important tool for debugging. Today’s oscilloscopes come with faster sampling rates, wider channel selection, higher resolutions and deep memory.

For instance, HDO8000 series introduced by Teledyne LeCroy has eight analogue input channels with 12-bit resolution. This allows engineers to view clean and crisp signals in greater detail, post debugging using digital channels. Often signals are lost in noise. But with high resolution, engineers can be sure of clearly seeing such signals, thereby improving the overall debug and analysis process.

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Some mixed-signal oscilloscopes available in the market
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RTO and RTE series of digital-storage oscilloscopes (DSOs) from Rohde & Schwarz, which also have the option of mixed-signal, provide high-resolution capabilities with their monolithic analogue-to-digital (A/D) converters that make acquisitions up to 16-bit resolution possible.

Engineers are always on the look out for more analogue channels in a scope. Eight analogue channels provide great flexibility to an engineer working on complex embedded designs. Although, more analogue channels on an MSO makes the device more expensive. Apart from Teledyne LeCroy’s HDO8000 series of MSOs, another test and measurement (T&M) vendor, Yokogawa, provides eight analogue channels in its DLM4000 series of MSOs.

Such MSOs, with a wide selection of channels, are ideal for professionals debugging high-power power electronics, automotive electronics and complex embedded as well as mechatronic designs. A unique ability of DLM400 series is that the eighth analogue channel comes with Flex MSO, a feature that converts it to an 8-bit logic analyser with the push of a button.

With more analogue channels and higher resolutions, deep record lengths is an equally important feature. T&M vendors are offering MSOs with deep memory typically ranging from 150Mpts per channel to 250Mpts per channel. The sampling rate for MSOs usually range from 1.5GSa/s to 4Gsa/s.

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CAN FD-enabled MSOs
Most of the known MSO vendors are steadily incorporating support for controller area network with flexible data rate (CAN FD) data frames by providing an additional trigger capability for better analysis of traffic in the CAN FD network.

After Teledyne LeCroy, Keysight and Rohde & Schwarz, Yokogawa has integrated support for CAN FD in their DLM2000 and DLM4000 series of MSOs. Evolution of more complex and advanced vehicular control systems has a proportional effect on the amount of traffic inside the CAN network. Therefore it is important for MSOs to have the ability to provide engineers with dedicated triggers and functionalities to boost the analysis and debugging process.

Apart from triggers and search functions for CAN FD, it is important for the MSO to have high memory depth as it makes it easier for the designer to handle extended data frames.

Some other oscilloscopes that support CAN FD are Infinii Vision 3000T X-series and 4000T X-series from Keysight Technologies, Teledyne LeCroy’s CAN FD TDM oscilloscopes, and RTE and RTO oscilloscopes from Rohde & Schwarz.

MSOs powered with PAM-4 analysis capability

F6A_boxMany known oscilloscope manufacturers have recently introduced pulse amplitude modulation (PAM-4) analysis capability in their range of MSOs.

Mobile computing applications are requiring ever-increasing Internet speeds as well as improved Internet infrastructure. To enable this, very-high-speed connectivity among server systems is absolutely necessary.

Non-return-to-zero (NRZ) encoding is mostly used for modulation in conventional communication methods. Industry experts feel NRZ will not function in a 56Gbit/s environment. Hence, one solution for this problem is to change the technique from NRZ to PAM. This would allow engineers to significantly expand the amount of data these can transmit across high-speed digital communication links. Many industry standards bodies are actively promoting PAM-4 technology.

PAM-4 signalling helps engineers to address design and measurement challenges swiftly and achieve faster time-to-market. Vendors usually provide an additional software tool that can be combined with particular models of MSOs to activate PAM-4 analysis capability.

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Recently, Keysight introduced Keysight N8827A PAM-4 analysis software (for V- and Z-series oscilloscopes) and N8827B PAM-4 analysis software (for S-series oscilloscopes), which engineers can use to perform a complete analysis of electrical PAM-4 signals.

Teledyne LeCroy too released a set of tools for similar analysis and they claim to be the only manufacturer who offer a software that compares jitter, eye and noise measurements on up to four lanes, simultaneously.

Serial-bus triggering trickling down to low-end MSOs
Another trend in MSOs is that serial-bus triggering and decoding is moving down to low-end MSOs. Earlier, only high-end MSOs had the capability of serial triggering, but it is slowly trickling down to basic MSOs offering 70MHz and 100MHz bandwidths.

“Designers of embedded systems operating at 20MHz and lower are addressing several applications including the IoT and wearable devices,” says Karl Chen, product manager, Rigol Technologies Inc. He adds, “This makes MSOs very affordable and provides great value, especially for designers working on a plethora of small- and mid-level embedded designs.”

For instance, MSO1000Z series from Rigol and SDS2000 series from Siglent provide serial triggering functions at an affordable price. See Table for pricing and other details.

Interesting developments in portable, pocket-sized MSOs
USB based tools used with PCs or laptops. When engineers look for flexibility, portability and ease of measurement, universal serial bus (USB) oscilloscopes prove to be a practical option.

USB MSOs are mostly used by engineers and technicians working in service, testing, equipment repair and manufacturing. Some MSOs are connected via USB, Ethernet or even RS232 and are widely used for a variety of applications starting from research and development (R&D) to embedded designs and educational purposes.

An MSO integrated with a protocol analyser enabled with USB 3.0 and Wi-Fi capabilities was recently introduced; a first of its kind in the PC based test instrument group.

USBee QX comes with a bandwidth of 600MHz and a combination of four analogue and 24 digital channels. One unique feature is that it can record 32 days of traces and display protocols as it has a buffer memory of 896 Msamples.

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An added benefit is that this device includes all popular serial protocols that usually need to be paid for separately in the case of benchtop MSOs.

Another option for hackers, hobbyists, students and engineers is a tool nearly the size of a Snickers chocolate bar. This device from BitScope comes with 20MHz bandwidth, which is apt for small- and, probably some, medium-level embedded applications. Completely user programmable, BitScope Micro also features two analogue channels and six digital channels. It also behaves as an 8-channel logic analyser, arbitrary waveform, a clock generator and spectrum analyser. In addition to Windows, Mac and Linux, it is also compatible with Raspberry Pi including its latest versions, Model A+ and Model B/B+.

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Tool specifically for Apple phones and tablets. An answer to test-bench tools with mobile and touchscreen advantage is Oscium’s iMSO-204L, a plug-and-play solution. Although specifically designed only for Apple devices, such solutions have become a viable alternative if engineers prefer to switch over to touch interface from traditional knobs.

These transform iPads or iPhones into a variety of test equipment tools like spectrum analysers, power meters, logic analysers and oscilloscopes. These are ultra-portable and small enough to fit in a pocket.

Bryan Lee, president, Oscium, says, “It is powered by the host device with less than 100mA of current (less than what it takes to power a small LED light), so there is very little impact to the battery life, eliminating the need for an external power source.”

He adds, “The software is very easy-to-use. It can be downloaded from Apple App Store and viewed in demo mode without access to hardware. After hardware is connected, field engineers can monitor, store, and email results while on-the-go.” He also claims that no other oscilloscope offers a solution quite like this unique system.

Quite recently, three software updates were made. As a result, users can now make advanced measurements between cursors, observe signal clips indicated by a colour change and can trigger in rolling mode.

Lee notes, “Not every user will be impacted by these changes but it demonstrates that we are continually investing in the tool and listening to our users.”


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