One Professor and Two Orderly Labs

Professor Wolfgang Matthes has taught microcontroller design, computer architecture, and electronics (both digital and analog) at the University of Applied Sciences in Dortmund, Germany, since 1992. He has developed peripheral subsystems for mainframe computers and conducted research related to special-purpose and universal computer architectures for the past 25 years.

When asked to share a description and images of his workspace with Circuit Cellar, he stressed that there are two labs to consider: the one at the University of Applied Sciences and Arts and the other in his home basement.

Here is what he had to say about the two labs and their equipment:

In both labs, rather conventional equipment is used. My regular duties are essentially concerned  with basic student education and hands-on training. Obviously, one does not need top-notch equipment for such comparatively humble purposes.

Student workplaces in the Dortmund lab are equipped for basic training in analog electronics.

Student workplaces in the Dortmund lab are equipped for basic training in analog electronics.

In adjacent rooms at the Dortmund lab, students pursue their own projects, working with soldering irons, screwdrivers, drills,  and other tools. Hence, these rooms are  occasionally called the blacksmith’s shop. Here two such workplaces are shown.

In adjacent rooms at the Dortmund lab, students pursue their own projects, working with soldering irons, screwdrivers, drills, and other tools. Hence, these rooms are occasionally called “the blacksmith’s shop.” Two such workstations are shown.

Oscilloscopes, function generators, multimeters, and power supplies are of an intermediate price range. I am fond of analog scopes, because they don’t lie. I wonder why neither well-established suppliers nor entrepreneurs see a business opportunity in offering quality analog scopes, something that could be likened to Rolex watches or Leica analog cameras.

The orderly lab at home is shown here.

The orderly lab in Matthes’s home is shown here.

Matthes prefers to build his  projects so that they are mechanically sturdy. So his lab is equipped appropriately.

Matthes prefers to build mechanically sturdy projects. So his lab is appropriately equipped.

Matthes, whose research interests include advanced computer architecture and embedded systems design, pursues a variety of projects in his workspace. He describes some of what goes on in his lab:

The projects comprise microcontroller hardware and software, analog and digital circuitry, and personal computers.

Personal computer projects are concerned with embedded systems, hardware add-ons, interfaces, and equipment for troubleshooting. For writing software, I prefer PowerBASIC. Those compilers generate executables, which run efficiently and show a small footprint. Besides, they allow for directly accessing the Windows API and switching to Assembler coding, if necessary.

Microcontroller software is done in Assembler and, if required, in C or BASIC (BASCOM). As the programming language of the toughest of the tough, Assembler comes second after wire [i.e., the soldering iron].

My research interests are directed at computer architecture, instruction sets, hardware, and interfaces between hardware and software. To pursue appropriate projects, programming at the machine level is mandatory. In student education, introductory courses begin with the basics of computer architecture and machine-level programming. However, Assembler programming is only taught at a level that is deemed necessary to understand the inner workings of the machine and to write small time-critical routines. The more sophisticated application programming is usually done in C.

Real work is shown here at the digital analog computer—bring-up and debugging of the master controller board. Each of the six microcontrollers is connected to a general-purpose human-interface module.

A digital analog computer in Matthes’s home lab works on master controller board bring-up and debugging. Each of the six microcontrollers is connected to a general-purpose human-interface module.

Additional photos of Matthes’s workspace and his embedded electronics and micrcontroller projects are available at his new website.

 

 

 

Quartus II Software Arria 10 Edition v14.0

Altera Corp. has released Quartus II software Arria 10 edition v14.0, which is an advanced 20-nm FPGA and SoC design environment. Quartus II software delivers fast compile times and enables high performance for 20-nm FPGA and SoC designs. You can further accelerate Arria 10 FPGA and SoC design cycles by using the range of 20-nm-optimized IP cores included in the latest software release.

Altera’s 20-nm design tools feature advanced algorithms. The Quartus II software Arria 10 edition v14.0 provides on average notably fast compile times. This productivity advantage enables you to shorten design iterations and rapidly close timing on 20-nm design.

Included in the latest software release is a full complement of 20-nm-optimized IP cores to enable faster design cycles. The IP portfolio includes standard protocol and memory interfaces, DSP and SoC IP cores. Altera also optimized its popular IP cores for Arria 10 FPGAs and SoCs, which include 100G Ethernet, 300G Interlaken, Interlaken Look-Aside, and PCI Express Gen3 IP. When implemented in Altera’s Arria 10 FPGAs and SoCs, these IP cores deliver the high performance.

The Quartus II software Arria 10 edition v14.0 is available now for download. The software is available as a subscription edition and includes a free 30-day trial. The annual software subscription is $2,995 for a node-locked PC license. Engineering samples of Arria 10 FPGAs are shipping today.

Source: Altera Corp.

Fast Quad IF DAC

ADI AD9144 16-bit 2.8 GSPS DAC - Fastest Quad IF DAC - High DynaThe AD9144 is a four-channel, 16-bit, 2.8-GSPS DAC that supports high data rates and ultra-wide signal bandwidth to enable wideband and multiband wireless applications. The DAC features 82-dBc spurious-free dynamic range (SFDR) and a 2.8-GSPS maximum sample rate, which permits multicarrier generation up to the Nyquist frequency.

With –164-dBm/Hz noise spectral density, the AD9144 enables higher dynamic range transmitters to be built. Its low SFDR and distortion design techniques provide high-quality synthesis of wideband signals from baseband to high intermediate frequencies. The DAC features a JESD204B eight-lane interface and low inherent latency of fewer than two DAC clock cycles. This simplifies hardware and software system design while permitting multichip synchronization.

The combination of programmable interpolation rate, high sample rates, and low power at 1.5 W provides flexibility when choosing DAC output frequencies. This is especially helpful in meeting four- to six-carrier Global System for Mobile Communications (GSM) transmission specifications and other communications standards. For six-carrier GSM intermodulation distortion (IMD), the AD9144 operates at 77 dBc at 75-MHz IF. Operating with the on-chip phase-locked loop (PLL) at a 30-MHz DAC output frequency, the AD9144 delivers a 76-dB adjacent-channel leakage ratio (ACLR) for four-carrier Wideband Code Division Multiple Access (WCDMA) applications.

The AD9144 includes integrated interpolation filters with selectable interpolation factors. The dual DAC data interface supports word and byte load, enabling users to reduce input pins on lower data rates to save board space, power, and cost.

The DAC is supported by an evaluation board with an FPGA Mezzanine Card (FMC) connector, software, tools, a SPI controller, and reference designs. Analog Devices’s VisualAnalog software package combines a powerful set of simulation and data analysis tools with a user-friendly graphical interface that enables users to customize their input signal and data analysis.

The AD9144BCPZ DAC costs $80. The AD9144-EBZ and AD9144-FMC-EBZ FMC evaluation boards cost $495.

Analog Devices, Inc.
www.analog.com

Closed-Loop Module

CogiscanThe LCR Control Module is a fully integrated and closed-loop system designed to eliminate the risk of placing incorrect passive components on PCBs. Combined with the Offline Job Setup and/or Line Setup Control module, the LCR Control Module’s software is integrated with an electrical LCR meter. The system verifies that the measured values (e.g., inductance, capacitance, resistance) are within the tolerances specified for the component. This electrical verification can be done at any time prior to mounting the reel on the placement machine.

Contact Cogiscan for pricing.

Cogiscan, Inc.
www.cogiscan.com

A Trace Tool for Embedded Systems

Tracing tools monitor what is going in a program’s execution by logging low-level and frequent events. Thus tracing can detect and help debug performance issues in embedded system applications.

In Circuit Cellar’s April issue, Thiadmer Riemersma describes his DIY tracing setup for small embedded systems. His system comprises three parts: a set of macros to include in the source files of a device under test (DUT), a PC workstation viewer that displays retrieved trace data, and a USB dongle that interfaces the DUT with the workstation.

Small embedded devices typically have limited-performance microcontrollers and scarce interfaces, so Riemersma’s tracing system uses only a single I/O pin on the microcontroller.

Designing a serial protocol that keeps data compact is also important. Riemersma, who develops embedded software for the products of his Netherlands-based company, CompuPhase, explains why:

Compactness of the information transferred from the embedded system to the workstation [which decodes and formats the trace information] is important because the I/O interface that is used for the transfer will probably be the bottleneck. Assuming you are transmitting trace messages bit by bit over a single pin using standard wire and 5- or 3.3-V logic levels, the transfer rate may be limited to roughly 100 Kbps.

My proposed trace protocol achieves compactness by sending numbers in binary, rather than as human-readable text. Common phrases can be sent as numeric message IDs. The trace viewer (or trace ‘listener’) can translate these message IDs back to the human-readable strings.

One important part of the system is the hardware interface—the trace dongle. Since many microcontrollers are designed with only those interfaces used for specific application needs, Riemersma says, typically the first step is finding a spare I/0 pin that can be used to implement the trace protocol.

In the following article excerpt, Riemersma describes his trace dongle and implementation requiring a single I/O pin on the microcontroller:

This is the trace dongle.

This is the trace dongle.

Photo 1 shows the trace dongle. To transmit serial data over a single pin, you need to use an asynchronous protocol. Instead of using a kind of (bit-banged) RS-232, I chose biphase encoding. Biphase encoding has the advantage of being a self-clocking and self-synchronizing protocol. This means that biphase encoding is simple to implement because timing is not critical. The RS-232 protocol requires timing to stay within a 3% error margin; however, biphase encoding is tolerant to timing errors of up to 20% per bit. And, since the protocol resynchronizes on each bit, error accumulation is not an issue.

Figure 1 shows the transitions to transmit an arbitrary binary value in biphase encoding—to be more specific, this variant is biphase mark coding. In the biphase encoding scheme, there is a transition at the start of each bit.

Figure 1: This is an example of a binary value transferred in biphase mark coding.

Figure 1: This is an example of a binary value transferred in biphase mark coding.

For a 1 bit there is also a transition halfway through the clock period. With a 0 bit, there is no extra transition. The absolute levels in biphase encoding are irrelevant, only the changes in the output line are important. In the previous example, the transmission starts with the idle state at a high logic level but ends in an idle state at a low logic level.

Listing 1 shows an example implementation to transmit a byte in biphase encoding over a single I/O pin. The listing refers to the trace_delay() and toggle_pin() functions (or macros). These system-dependent functions must be implemented on the DUT. The trace_delay() function should create a short delay, but not shorter than 5 µs (and not longer than 50 ms). The toggle_pin() function must toggle the output pin from low to high or from high to low.

For each bit, the function in Listing 1 inverts the pin and invokes trace_delay() twice. However, if the bit is a 1, it inverts the pin again between the two delay periods. Therefore, a bit’s clock cycle takes two basic “delay periods.”

Listing 1: Transmitting a byte in biphase encoding, based on a function to toggle an I/O pin, is shown.

Listing 1: Transmitting a byte in biphase encoding, based on a function to toggle an I/O pin, is shown.

The biphase encoding signal goes from the DUT to a trace dongle. The dongle decodes the signal and forwards it as serial data from a virtual RS-232 port to the workstation (see Photo 2 and the circuit in Figure 2).

Photo 2: The trace dongle is inserted into a laptop and connected to the DUT.

Photo 2: The trace dongle is inserted into a laptop and connected to the DUT.

This trace dongle interprets biphase encoding.

Figure 2: This trace dongle interprets biphase encoding.

The buffer is there to protect the microcontroller’s input pin from spikes and to translate the DUT’s logic levels to 5-V TTL levels. I wanted the trace dongle to work whether the DUT used 3-, 3.3-, or 5-V logic. I used a buffer with a Schmitt trigger to avoid the “output high” level of the DUT at 3-V logic, plus noise picked up by the test cable would fall in the undefined area of 5-V TTL input.

Regarding the inductor, the USB interface provides 5 V and the electronics run at 5 V. There isn’t room for a voltage regulator. Since the USB power comes from a PC, I assumed it might not be a “clean” voltage. I used the LC filter to reduce noise on the power line.

The trace dongle uses a Future Technology Devices International (FTDI) FT232RL USB-to-RS-232 converter and a Microchip Technology PIC16F1824 microcontroller. The main reason I chose the FT232RL converter is FTDI’s excellent drivers for multiple OSes. True, your favorite OS already comes with a driver for virtual serial ports, but it is adequate at best. The FTDI drivers offer lower latency and a flexible API. With these drivers, the timestamps displayed in the trace viewers are as accurate as what can be achieved with the USB protocol, typically within 2 ms.

I chose the PIC microcontroller for its low cost and low pin count. I selected the PIC16F1824 because I had used it in an earlier project and I had several on hand. The microcontroller runs on a 12-MHz clock that is provided by the FTDI chip.

The pins to connect to the DUT are a ground and a data line. The data line is terminated at 120 Ω to match the impedance of the wire between the dongle and the DUT.

The cable between the DUT and the trace dongle may be fairly long; therefore signal reflections in the cable should be considered even for relatively low transmission speeds of roughly 250 kHz. That cable is typically just loose wire. The impedance of loose wire varies, but 120 Ω is a good approximate value.

The data line can handle 3-to-5-V logic voltages. Voltages up to 9 V do not harm the dongle because it is protected with a Zener diode (the 9-V limit is due to the selected Zener diode’s maximum power dissipation). The data line has a 10-kΩ to 5-V pull-up, so you can use it on an open-collector output.

The last item of interest in the circuit is a bicolor LED that is simply an indicator for the trace dongle’s status and activity. The LED illuminates red when the dongle is “idle” (i.e., it has been enumerated by the OS). It illuminates green when biphase encoded data is being received.

After the dongle is built, it must be programmed. First, the FT232RL must be programmed (with FTDI’s “FT Prog” program) to provide a 12-MHz clock on Pin C0. The “Product Description” in the USB string descriptors should be set to “tracedongle” so the trace viewers can find the dongle among other FTDI devices (if any). To avoid the dongle being listed as a serial port, I also set the option to only load the FTDI D2XX drivers.

To upload the firmware in the PIC microcontroller, you need a programmer (e.g., Microchip Technology’s PICkit) and a Tag-Connect cable, which eliminates the need for a six-pin header on the PCB, so it saves board space and cost.

The rest of the article provides details of how to create the dongle firmware, how to add trace statements to the DUT software being monitored, and how to use the GUI version of the trace viewer.

The tracing system is complete, but it can be enhanced, Riemersma says. “Future improvements to the tracing system would include the ability to draw graphs (e.g., for task switches or queue capacity) or a way to get higher precision timestamps of received trace packets,” he says.

For Riemersma’s full article, refer to our April issue now available for membership download or single-issue purchase.