An Education on SoC using Verilog

[Bruce Land] is one of those rare individuals who has his own Hackaday tag. He and his students at Cornell have produced many projects over the years that have appeared on these pages, lately with FPGA-related projects. If you only know [Land] from projects, you are missing out. He posts lectures from many of his classes and recently added a series of new lectures about developing with a DE1 System on Chip (SoC) using an Altera Cyclone FPGA using Verilog. You can catch the ten lectures on YouTube.

The class material is different for 2017, so the content is fresh and relevant. The DE1-SOC has a dual ARM processor and boots Linux from an SD card. There are several labs and quite a bit of background material. The first lab involves driving a VGA monitor. Another is a hardware solver for ordinary differential equations.

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Everything’s a Touch Surface with Electrick

Touch screens are great, but big touchscreens are expensive and irregular touchscreens are not easy to make at all. Electrik is a method developed by several researchers at Carnegie Mellon University that makes almost any solid object into a touch surface using tomography. The catch is that a conductive coating — in the form of conductive sheets, 3D plastic, or paint — is necessary. You can see a demonstration and many unique applications in the video below. They’ve even made a touch-sensitive brain out of Jell-O and a touchable snowman out of Play-Doh.

The concept is simple. Multiple electrodes surround the surface. The system injects a current using a pair of electrodes and then senses the output at the other terminals. A finger touch will change the output of several of the electrodes. Upon detection, the system will change the injection electrodes and repeat the sensing. By using multiple electrode pairs and tomography techniques, the system can determine the location of touch and even do rough motion tracking like a low-resolution touch pad mouse.

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Logic Analyzer on Chips

The Internet is full of low-speed logic analyzer designs that use a CPU. There are also quite a few FPGA-based designs. Both have advantages and disadvantages. FPGAs are fast and can handle lots of data at once. But CPUs often have more memory and it is simpler to perform I/O back to, say, a host computer. [Mohammad] sidestepped the choice. He built a logic analyzer that resides partly on an FPGA and partly on an ARM processor.

In fact, his rationale was to replace built-in FPGA logic analyzers like Chipscope and SignalTap. These are made to coexist with your FPGA design, but [Mohammad] found they had limitations. They also eat up die space you might want for your own design, so by necessity, they probably don’t have much memory.

The system can capture and display 32-bit signals on a 640×480 VGA monitor in real-time. The system also has a USB mouse interface which is used to zoom and scroll the display. You can see a video of the thing in operation, below.

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MATLAB and Simulink for Zynq

Although we see a lot of MATLAB use in industry and in academia, it isn’t as popular in the hacker community. That’s probably due to the cost. If you’ve ever wondered why companies will pay over $2000 for the base product, you might enjoy the video of a webinar covering using MATLAB and Simulink (a companion product) to program the CPU and FPGA on a Zynq Zedboard. Not interested because of the price? If you aren’t using it for commercial purposes, it isn’t as bad as you think.

MathWorks is one of those companies that likes to market by virtually giving away products to students with the hope that they’ll adopt the same tools when they land jobs in industry. Their flagship product, MATLAB, is well-entrenched in the labs and offices of big corporations. We’ve often thought that MATLAB is sort of what FORTRAN would look like if it had been developed in the last 20 years instead of 60 years ago. It is true that a base license for MATLAB is over $2000. However, if you aren’t using it for commercial purposes, and you can’t score a student license, you can get a personal license of MATLAB for about $150. The extra modules are also similarly reduced in price. If you are a student, the price drops to about $100, although many schools have licenses students can use at no cost to them.

If you watch the video from [Noam Levine], you’ll see you get your money’s worth. If you are wanting to configure the FPGA directly, this isn’t for you. But if you just want to accelerate a program by pushing DSP or other algorithms that can benefit from hardware assistance, MATLAB makes it very easy.

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Rusty ARM

You’ve probably heard that Rust is a systems programming language that has quite the following growing. It purports to be fast like C, but has features like guaranteed memory and thread safety, generics, and it prevents segmentation faults. Sounds like just the thing for an embedded system, right? [Jorge Aparicio] was frustrated because his CPU of choice, an STM32 ARM Cortex-M didn’t have native support for Rust.

Apparently, you can easily bind C functions into a Rust program but that wasn’t what he was after. So he set out to build pure Rust programs that could access the device’s hardware and he documented the effort.

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STM32 Analog Converter Phase Noise

[Avian] has been using STM32 ARM processors to sample RF for a variety of applications. At first, he was receiving relatively wide TV signals. Recently, though, he’s started dealing with very narrow signals and he found that his samples had a lot of spread in the frequency domain that he didn’t expect.

What followed was some detective work that resulted in a determination that phase noise was the culprit. But why? [Avian] took some measurements and noticed that the phase noise almost exactly matched the phase noise specification for the STM32’s phase locked loop (PLL).

Unfortunately, there didn’t seem to be a good way to avoid using the PLL without major changes to the rest of the circuit. However, it was quite the learning experience and something to be aware of when counting on built-in converters for high-accuracy measurements.

One of the best things about this post is the references to more information. There’s a great explanation of phase noise, as well as a specific application note about clock jitter and analog converters.

We’ve talked about phase noise in direct digital synthesis a few times. But usually, it is pretty obvious like when you are asking a CPU to double as an RF transmitter. [Avian’s] post was a bit more of a detective story.

Adding a debugger to a Teensy 3.5/3.6

The Teensy is a powerful ARM-based development board with loads of features that can do fun stuff with USB as well. Like many dev boards, it uses a less powerful processor as an interface. Teensy designer [Paul Stoffregen] added a debug header to allow direct SWD JTAG access to the main chip, but the interface microcontroller has to be silenced for that to work, and the code to do so is still in progress.

Impatient, [Erich Styger] documents the changes he made to add support for the J-Link SWD protocol by removing the offending NXP Kinetis KL02Z that serves as the as the onboard interface and bootloader that helps the Arduino IDE talk to the K64F which is the main chip. After the KL02Z was removed, [Erich] populated the debug headers and then wired up the Segger J-Link to the board and tested it out with Eclipse, GDB, and standard SWD debug tools.

The end result is a Cortex M4F board that can work with standard tools at a third of the price of the Kinetis’ development board. [Paul Stoffregen] confirms that the debugging functionality will be added to the bootloader code soon but until then, a hardware hack is a working, if brutal, approach to debugging on the platform.

More information on the JTAG interface is available for the interested. And if Teensy isn’t your thing, you might consider an STM32-based development board.