In this blog, I will be looking at the Digilent Analog Discovery Pro ADP3450 and how it compares with other products on the market. I will also be looking at what is unique about the ADP3450 and who it might appeal to.
Feature Introduction
The Digilent Analog Discovery Pro ADP3450 is predominantly advertised as a four-channel mixed-signal (or mixed-domain) oscilloscope. Such a device is not only capable of analog measurements but also digital measurements, and would operate in both time (oscilloscope) and frequency (spectrum) domains. It is part of the 3000-series, with a two-channel version carrying the model number ADP3250. At the time of publication, the ADP3450 is listed (on element14 Australia) for a price of AU$2150.83 excl. GST for the base kit or AU$2414.91 excl. GST for a kit including probes and test clips. The two-channel version is listed for AU$1486.48 excl. GST and AU$1650.91 excl. GST respectively.
The brochure claims that the Analog Discovery Pro 3000 series “provide the utility of professional benchtop equipment with the flexibility of a portable instrument.” As a test instrument, it is somewhat unique as a multi-instrument device, consisting of four-channels of oscilloscope input capable of 125MSPS at 14-bits with 55MHz bandwidth, two-channels of arbitrary waveform generator output capable of 125MSPS at 14-bits up to +/-5V swing, 16-channels of digital I/O (not just input) with two trigger I/O ports (again, not just input or output). However, with these ports, it claims to offer much more, including the capability of being a network analyser, spectrum analyser, voltmeter, impedance analyser, data logger, logic analyser, pattern generator, protocol analyser and more. Furthermore, the instrument is connected by USB 2.0 and Gigabit Ethernet, with four USB 2.0 device ports to support peripherals such as supported Wi-Fi adapters for wireless connectivity and mass storage devices, plus the capability of “Linux Mode” operation independent of a connected host.
It traces its heritage to the earlier Digilent Analog Discovery and Digilent Analog Discovery 2 boards which were designed as low-cost, textbook-priced USB-powered multi-instrument devices for educational use. These instruments were not necessarily comparable to benchtop big-box instruments on specifications, but did enable new lab-in-a-box and take-home-labs applications while providing enough capabilities to perform debugging and measurements on simple circuits at modest operating frequencies. It seemed to be a collaboration with the units co-branded with Xilinx and Analog Devices logos, as the designs used ICs predominantly from the two companies. The strength of those devices was the Digilent WaveForms software which integrated the multiple instruments to offer more sophisticated measurement capabilities without the need for sophisticated programming, while also offering an SDK so that those who wished to automate the instruments for custom applications could do so. This tradition is carried forward into the Analog Discovery Pro line which continues the use of the WaveForms software and SDK.
Compared to the original Analog Discovery and Analog Discovery 2, the Analog Discovery Pro ADP3450 is notably more expensive and is not as compact, being physically larger and requiring an external power supply. It does, however, do away with a number of frustrations with the original Analog Discovery and Analog Discovery 2 by offering proper BNC ports for probes and wider bandwidth. I suspect the higher price is targeting educational institutions instead, who may choose to loan out these units rather than require their students to purchase their own, or choose to stock-up their own lab benches with these to replace ageing or unsupported lab hardware. The relatively compact size and low weight compared to traditional instruments is still very much an asset in favour of the ADP3450. Perhaps it may also find a market for final-year undergraduate or research students who may be doing experiments in the field, require a more flexible test device or do not have the budget for big-brand big-box units but also may benefit from the tight integration of the multiple instruments. A key flexibility is the digital I/O being truly I/O, as it allows the unit not only to sniff, but also to participate in bus transactions. Another is the Linux Mode capabilities with Ethernet connectivity, allowing the instrument to essentially operate independently of the host – something very few instruments can do.
For true professionals, however, the specifications seem much less appealing – for example, the 55MHz bandwidth is nothing particularly exciting, nor is the 15MHz waveform generator bandwidth. Any spectrum analysis or impedance analysis would need to stay within these parameters, which is not competitive with dedicated instruments. The supported protocol decode for SPI, I2C, UART, CAN, I2S, 1-Wire, HDMI CEC, and Manchester Encoding is somewhat lacking compared to some other options on the market. The buffer memory (e.g. oscilloscope - 32,768 samples per channel ordinarily, 65,536 samples per channel in extended, 128MS across all channels in record mode) is particularly small in normal operating modes and the input has only two “real” voltage ranges, although the 14-bit resolution is quite an improvement over the 8-bits offered by most other instruments. While the claim of “no misleading specs” is true, there are many important specifications found on standalone test equipment that is not provided for the ADP3450 – for example, input cross-talk figures, input noise-floor, effective number of bits, channel-to-channel skew, etc.
Market Survey Comparison
Thankfully, for the ADP3450, the market for USB-connected host-driven instruments (as opposed to standalone benchtop big-box instruments) is relatively small and fragmented. This market gets much smaller when we focus on mixed-signal/mixed-domain capable devices, preferably those with four analog channels. Over time, there have been many attempts at low-cost USB oscilloscopes with very few being particularly successful with the exception of Picoscope, who I see as the main contender.
As a Picoscope user myself, I can definitely say with confidence that the Picoscope software is quite user-friendly and the units generally perform well. I have met some limitations over time, for example, not being able to trigger on bus decoding which makes continuous loss-free bus decoding difficult, but they are not unexpected. Within this price range, perhaps the closest contender is the Picoscope 3404D MSO (AU$1948.95 excl. GST) which offers four channels of analog input at 8-bit 1GSPS with 70MHz bandwidth, 16-channels of digital input, a single 20MSPS 12-bit arbitrary waveform generator with >1MHz bandwidth and 128MS of buffer memory. It even comes with all probes included and can operate from USB bus power. For a little more, one could step up to the 3405D MSO (AU$2516.25 excl. GST) and have 100MHz analog bandwidth and 256MS of buffer memory or the 3406D MSO (AU$3303.15 excl. GST) for 200MHz of analog bandwidth and 512MS of buffer memory. I actually have a 3406D MSO myself which I use for field work and it has been quite useful. The Picoscope is known for its wide protocol decoding support and has a faster USB3.0 interface, but compared to the ADP3450, it doesn’t have Ethernet, Wi-Fi, Linux Mode, pattern generator, digital I/O capabilities and does not integrate the use of the AWG and oscilloscope channels to perform impedance analysis. Both have the possibility of automation development as both offer their own SDKs. There are higher-end units from Picoscope, but the prices escalate quickly out of reach.
Outside of Picoscope, perhaps the next most interesting MSO I found was from PeryTech. Their MSO-40xxx series (MSO-40161,2,322,325,326) have only two analog channels, but have sampling rates of up to 400MS/s, 8-bit resolution, 100MHz bandwidth on the analog, but 16 or 32 digital channels with 64kS-2MS memory depth plus up to 1M:1 compression. It has one of the longest protocol decode lists I’ve ever seen - I2C, SPI, UART, I2S, PS2, 1-Wire, USB 1.1, S/PDIF, SD 1.1/2.0, CAN Bus,Lin Bus,3-Wire, Microwire, SSI, Miller, Manchester, SM Bus, PM Bus, Modbus, Jtag, DMX512, LPC, SWD, HDLC, RC-5, ESPI, Wiegand, QI, HDMI CEC, MII/RMII/GMII, DALI, GPIB, UNI/O, MIDI, FlexRay. This unit is connected via USB 2.0 but has software which looks very shabby by comparison and there is no arbitrary waveform generation capability. The MSO-40162 which is perhaps the closest match has a price of about AU$500 which is excellent value for money, but I have many reservations about the software and true specifications of the unit.
Another previously available option is the Link Instruments MSO-28, a two-channel 200MSPS analog input with 60MHz bandwidth and eight channel digital logic analyser supporting SPI and I2C. This unit is bus-powered and connects via USB 2.0, however, it seems to be a low-end instrument with misleading 2GSa/s printing when that only applies for repetitive signals and just 1kS memory buffer. Regardless, it was widely available at a time for around AU$450, which makes the PeryTech looks amazing by comparison. It is no competition for the ADP3450.
The PoScope Mega50 from PoLabs is another USB 2.0 connected instrument that I have had experience with. It offers 2 analog channels at 48MSPS with 8-bit resolution, 16 digital channels with UART, I2C, SPI and 1-Wire decoding and a signal generator up to 12.5kHz. This is more of a “starter” measurement device rather than an actual serious test and measurement instrument, but the bundle complete with probes costs about AU$180. This is more of a competition with the original Analog Discovery (or the Analog Discovery 2 which replaces it) than it is with the ADP3450, but this speaks to the lack of serious options in this market.
Of course, one can go even further, down to a PCB-sized solution like the Espotek Labrador which offers a 2-channel 750kSPS oscilloscope, 2-channel 1MSPS waveform generator, power supply, two-channel logic analyser at 3MSPS with serial decoding and multimeter for about AUD$40. Such devices are not true pieces of test equipment, but fill a niche especially during COVID-19 lockdowns where the need for remote learning labs means that sacrifices have to be made to allow each student to have their own basic test equipment for the purposes of education.
For educators looking at all-in-one benchtop solutions, the National Instruments ELVIS has been the mainstay of some electrical engineering laboratories. The latest NI ELVIS III starts at AU$5,588 without any accessories, which is quite a noticeable jump over the ADP3450, however, the main appeal is not the instruments but the integration of various “device” cards and laboratory exercises that can be performed using such a device. Another option is the Digilent Analog Discovery Pro ADP5250 which looks like a bigger brother to the ADP3450, being fan-cooled and requiring power connected directly into the unit. The ADP5250 doesn’t appear to have the USB-host ports, Ethernet or Linux mode, and has only half the oscilloscope, arbitrary waveform generator, trigger channels and digital I/O channels. In return, it adds on a digital logic analyser offering 32 channels, provides a “real” multi-rail power supply and a digital multimeter. From this thread, it seems that this is a rebranding of the NI VirtualBench VB-8012 with support added to WaveForms. Accordingly, it lists for about AU$4515 excl. GST which is also significantly more than the ADP3450.
Conclusion
The Digilent Analog Discovery Pro ADP3450 is a four-channel mixed-signal (or mixed-domain) oscilloscope capable of analog and digital measurements in both time and frequency domains. At the time of publication, the ADP3450 is listed (on element14 Australia) for a price of AU$2150.83 excl. GST for the base kit or AU$2414.91 excl. GST for a kit including probes and test clips.
As a test instrument, it is somewhat unique as a multi-instrument device, consisting of four-channels of oscilloscope input capable of 125MSPS at 14-bits with 55MHz bandwidth, two-channels of arbitrary waveform generator output capable of 125MSPS at 14-bits up to +/-5V swing, 16-channels of digital I/O (not just input) with two trigger I/O ports (again, not just input or output). However, with these ports, it claims to offer much more, including the capability of being a network analyser, spectrum analyser, voltmeter, impedance analyser, data logger, logic analyser, pattern generator, protocol analyser and more through the Digilent WaveForms software with SDK. Furthermore, the instrument is connected by USB 2.0 and Gigabit Ethernet, with four USB 2.0 device ports to support peripherals such as supported Wi-Fi adapters for wireless connectivity and mass storage devices, plus the capability of “Linux Mode” operation independent of a connected host.
Compared to the Analog Discovery 2, the Analog Discovery Pro ADP3450 is more expensive, not as compact, and requires an external power supply. In return, it offers proper BNC ports for probes and wider bandwidth. Perhaps it may appeal to students who may be doing field experiments, require a flexible test device or do not have the budget for big-brand big-box units but may benefit from the tight integration of the multiple instruments. A key flexibility is the digital I/O being truly I/O, as it allows the unit not only to sniff, but also to participate in bus transactions. Another is the Linux Mode capabilities with Ethernet connectivity, allowing the instrument to essentially operate independently of the host – something very few instruments can do.
For true professionals, however, the specifications seem much less appealing – for example, the 55MHz bandwidth is nothing particularly exciting, nor is the 15MHz waveform generator bandwidth. The supported protocol decode is somewhat lacking compared to some other options on the market. The buffer memory (e.g. oscilloscope – 32kS per channel ordinarily, 64kS per channel in extended, 128MS across all channels in record mode) is particularly and the input has only two “real” voltage ranges, although the 14-bit resolution is quite an improvement over the 8-bits offered by others. The ADP3450’s specifications also lack some important values – for example, input cross-talk figures, input noise-floor, effective number of bits, channel-to-channel skew, etc.
The market for USB-connected host-driven instruments is relatively small and fragmented, with many attempts but very few successes, especially in the mixed-signal/mixed-domain area. Perhaps the closest contender is the Picoscope 3404D MSO (AU$1948.95 excl. GST) which offers four channels of analog input at 8-bit 1GSPS with 70MHz bandwidth, 16-channels of digital input, a single 20MSPS 12-bit arbitrary waveform generator with >1MHz bandwidth and 128MS of buffer memory. It even comes with all probes included and can operate from USB bus power. For a little more, one could step up to the 3405D MSO (AU$2516.25 excl. GST) and have 100MHz analog bandwidth and 256MS of buffer memory or the 3406D MSO (AU$3303.15 excl. GST) for 200MHz of analog bandwidth and 512MS of buffer memory. The Picoscope is known for its wide protocol decoding support and has a faster USB3.0 interface, but compared to the ADP3450, it doesn’t have Ethernet, Wi-Fi, Linux Mode, pattern generator, digital I/O capabilities and does not integrate the use of the AWG and oscilloscope channels to perform impedance analysis.
For educators looking at all-in-one benchtop solutions, the latest NI ELVIS III starts at AU$5,588 without any accessories, which is quite a noticeable jump over the ADP3450. Another option is the Digilent Analog Discovery Pro ADP5250 which doesn’t have the USB-host ports, Ethernet or Linux mode, and has only half the oscilloscope, arbitrary waveform generator, trigger channels and digital I/O channels. In return, it adds on a digital logic analyser offering 32 channels, provides a “real” multi-rail power supply and a digital multimeter. Accordingly, it lists for about AU$4515 excl. GST which is also significantly more than the ADP3450.
The ADP3450 is thus quite a unique multi-instrument combination device. While its price is not as inexpensive as the Analog Discovery 2, it is still priced competitively once the number of instruments and specifications are taken into account. As purely a measurement instrument, the paper specifications may not appeal to the professionals, but it hides the fact that the ADP3450 is much more tightly integrated than other instruments thus offering features such as impedance analysis and is simultaneously more flexible in being able to operate independently of a host in Linux Mode with its SDK. It is also not only capable of digital bus sniffing, but can also perform true I/O and participate in digital buses, making it even more versatile than most digital-capable instruments. This makes it especially well-suited for educational, experimentation and hacking purposes. It seems to have an upper edge when it comes to ADC resolution, although this comes at the cost of sample rate and bandwidth and the WaveForms software may be an asset where users are already familiar with it from previous experience with the Analog Discovery 2. In the education space, it is cheaper than the other bench-top options while also being small enough to be portable, thus perhaps could make an ideal instrument to loan out to students for them to catch-up on labs at home. Likewise, final-year or research students without the budget for a plethora of big-box instruments could consider this as a piece of test equipment that may still be sufficient even after they graduate.
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This post is a part of the Digilent Analog Discovery Pro ADP3450 USB/Ethernet Mixed Signal Oscilloscope RoadTest Review.
