Fit Sixteen (or more) Asynchronous Serial Receivers into the Area of a Standard UART Receiver
Michael Morris shows how to pack many asynchronous serial receivers into the area of a single UART by treating FPGA LUTs as writable storage and sharing logic. Using a 4-bit channel counter, microprogrammed state machine, and time-multiplexed baud/sample resources, he fits 16 receive channels (12 used for Caller ID) into a Spartan II XC2S30 and explains input synchronization, filtering, and the multi-channel FIFO approach.
Use Microprogramming to Save Resources and Increase Functionality
Microprogramming can rescue an overfull FPGA, Michael Morris shows, by compressing control logic and time-multiplexing FIFO storage. He replaces an ABEL state machine with a small microprogram ROM that uses block RAM for deep Rx/Tx FIFOs and LUT RAM for pointers and counters, freeing about 25 percent of the device. The article includes Verilog comparisons, resource tables, and a microassembler link to reproduce the approach.
I don’t often convert VHDL to Verilog but when I do ...
Converting VHDL to Verilog is tedious, and Christopher Felton lays out a pragmatic, repeatable workflow using vhd2vl to do most of the heavy lifting. He walks through the iterate-run-comment-fix cycle, highlights frequent failure points like arrays, records and packages, and explains why many open-source projects favor Verilog for better FOSS simulator support.
Point of View
Christopher defends a straightforward MyHDL RTL description of a FIR filter, arguing it is explicit, readable, and concise. He compares that style to a functional hardware description built with Python primitives and list comprehensions, and finds both convert to identical synthesis resources for this example. The post highlights readability tradeoffs and suggests choice often comes down to background and preference.
MyHDL Presentation Examples
Christopher Felton collected slide-ready MyHDL demos he used at EELive and PyOhio, making it easy to see practical HDL examples in action. The post explains the tradeoffs behind single-slide examples, links to 2013 and 2014 demos from simple FPGA hello-worlds to filters and a VGA system, and points readers to the repository where full and larger examples live for reuse.
Spline interpolation
Markus Nentwig provides a cookbook for segmented cubic spline interpolation that turns scattered or noisy data into efficient fixed-point functions. The article shows how to build third-order polynomial segments with explicit value and slope control via basis functions, solve scaling factors by least-squares in Octave/Matlab, and export coefficients for Verilog RTL evaluation using the Horner scheme and practical fixed-point tips.
[Comments] C HLS Benefits
Christopher Felton argues C-to-gate HLS showed little advantage in his median calculation comparison with MyHDL. He explains the test mixes language paradigm and abstraction: Vivado C HLS is an imperative, step-by-step style while MyHDL offers a concurrent, HDL-level description with Python's readability and elaboration features. He notes C-HLS can help if you only know C, but for massively parallel FPGA work non-C tools may be preferable.
Little to no benefit from C based HLS
Christopher shows why C-based HLS delivers little practical benefit compared with a MyHDL RTL approach, using a Vivado HLS median-filter example. He walks through the sort-network median, compares C and MyHDL implementations, and argues MyHDL is as concise while providing clearer microarchitecture control. The post emphasizes that choosing the right algorithm is the hard part, and HLS won’t replace hardware understanding.
Signed serial-/parallel multiplication
Struggling with costly wide adders for signed multiplication on FPGAs? Markus Nentwig unpacks a neat bit-level trick that turns two's-complement signed-signed multiplication into a serial-parallel routine using only a one-bit wider adder. Learn how flipping sign bits and a small, controlled constant cancel lets you avoid full sign-extension, and get a parametrized Verilog RTL plus synthesis notes to try it yourself.
MyHDL Interface Example
Christopher Felton shows how MyHDL 0.9 interfaces bundle Signals into a single bus object to cut connector clutter and simplify module connections. The post walks through a pedagogical example where button presses drive a memory-mapped BareBoneBus read-modify-write that inverts LEDs, with a TDD-style testbench and notes on converting to Verilog/VHDL and loading the example on supported boards.
Fit Sixteen (or more) Asynchronous Serial Receivers into the Area of a Standard UART Receiver
Michael Morris shows how to pack many asynchronous serial receivers into the area of a single UART by treating FPGA LUTs as writable storage and sharing logic. Using a 4-bit channel counter, microprogrammed state machine, and time-multiplexed baud/sample resources, he fits 16 receive channels (12 used for Caller ID) into a Spartan II XC2S30 and explains input synchronization, filtering, and the multi-channel FIFO approach.
Launch of EmbeddedRelated.tv
Stephane Boucher launches EmbeddedRelated.tv to host live broadcasts from Embedded World, starting next week. The site will show a constantly evolving schedule, a Live! tab to find ongoing streams, and ad-hoc demos added from the show floor. Expect schedule conflicts and small hiccups, and plan to refresh the page and join the forum thread for real-time updates and feedback.
Feedback Controllers - Making Hardware with Firmware. Part 9. Closing the low-latency loop
This article demonstrates combining DSP and feedback-control on an Intel Cyclone floating-point FPGA to build low-latency closed-loop circuit emulators and controllers. Using a single floating-point biquad at 1.6 Msps, an IFFT multi-tone 4.096 ms capture for wideband measurement, and MATLAB references for verification, the author achieves sub-nanosecond timing insight and applies DSP phase compensation to cancel about 100 pF of PCB parasitics.
Project introduction: Digital Filter Blocks in MyHDL and their integration in pyFDA
Sriyash Caculo is building a bridge between filter design and hardware by implementing digital filter blocks in MyHDL and integrating them with PyFDA as part of a Google Summer of Code project. The work aims to convert PyFDA floating point designs into fixed point MyHDL blocks that automatically generate VHDL or Verilog, with tests and tutorials to ensure correctness and usability.
Feedback Controllers - Making Hardware with Firmware. Part 3. Sampled Data Aspects
This article digs into practical sampled-data issues you must address when building feedback controllers for circuit emulation. It highlights a common MATLAB versus Simulink discrepancy caused by DAC holding, explains why FOH (ramp-invariant) c2d conversion matters, and surveys latency, bit depth, filter and precision trade-offs. It also lists candidate ADCs, DACs and FPGAs used in a real evaluation platform to guide hardware choices.
Helping New Bloggers to Break the Ice: A New Ipad Pro for the Author with the Best Article!
Breaking the ice can be tough. Over the years, many individuals have asked to be given access to the blogging interface only to never post an article.
Feedback Controllers - Making Hardware with Firmware. Part I. Introduction
This first post kicks off a series on using DSP and feedback control with mixed-signal electronics and FPGAs to emulate two-terminal circuits and create low latency controllers. It frames circuit emulation as a feedback problem, highlights latency as the key practical constraint, and outlines the planned evaluation hardware, target devices, and software tools that will be used in later MATLAB/Simulink and FPGA work.
Use Microprogramming to Save Resources and Increase Functionality
Microprogramming can rescue an overfull FPGA, Michael Morris shows, by compressing control logic and time-multiplexing FIFO storage. He replaces an ABEL state machine with a small microprogram ROM that uses block RAM for deep Rx/Tx FIFOs and LUT RAM for pointers and counters, freeing about 25 percent of the device. The article includes Verilog comparisons, resource tables, and a microassembler link to reproduce the approach.
Feedback Controllers - Making Hardware with Firmware. Part 5. Some FPGA Aspects.
This installment digs into practical FPGA choices and board-level issues for a low-latency, floating-point feedback controller. It compares a Cyclone V implementation against an older SHARC-based design, quantifies the tradeoff between raw DSP resources and cycle latency, and calls out Gotchas found on the BeMicro CV A9 evaluation card. Engineers get concrete prompts for where to optimize: clocking, DSP-block use, I/O standards, and algorithm partitioning.
Developing FPGA-DSP IP with Python
Designing FPGA-DSP IP entirely in Python is practical and productive, as Christopher Felton demonstrates using MyHDL. He shows how numpy and scipy handle the signal design while a SIIR class generates RTL, enables side-by-side floating-point and HDL simulation, and converts to Verilog for synthesis. The post includes Xilinx XC3S500E resource results and a link to the SIIR source on BitBucket, making it easy to try the workflow.
Who else is going to Sensors Expo in San Jose? Looking for roommate(s)!
This will be my first time attending this show and I must say that I am excited. I am bringing with me my cameras and other video equipment with the intention to capture as much footage as possible and produce a (hopefully) fun to watch 'highlights' video. I will also try to film as many demos as possible and share them with you.
I enjoy going to shows like this one as it gives me the opportunity to get out of my home-office (from where I manage and run the *Related sites) and actually...
Launch of EmbeddedRelated.tv
Stephane Boucher launches EmbeddedRelated.tv to host live broadcasts from Embedded World, starting next week. The site will show a constantly evolving schedule, a Live! tab to find ongoing streams, and ad-hoc demos added from the show floor. Expect schedule conflicts and small hiccups, and plan to refresh the page and join the forum thread for real-time updates and feedback.
3 Good News
Stephane Boucher reports three quick wins for the EmbeddedRelated community: two sponsors have seeded a $1,000 rewards pool, the site now serves all pages over HTTPS, and the new forums have their first active discussions. If you want a share of the sponsor-funded rewards, jump into the forums and check the Vendors Directory for opportunities. Stay tuned for more updates.
Ancient History
The other day I was downloading an IDE for a new (to me) OS. When I went to compile some sample code, it failed. I went onto a forum, where I was told "if you read the release notes you'd know that the peripheral libraries are in a legacy download". Well damn! Looking back at my previous versions I realized I must have done that and forgotten about it. Everything changes, and keeping up with it takes time and effort.
When I first started with microprocessors we...
What to See at Embedded World 2019
Skip the overwhelm at Embedded World 2019, Stephane Boucher lays out a practical preview of what to see and how to prioritize your time. The post helps embedded engineers focus on demos, vendor booths, and sessions that matter without getting lost on the show floor. Read it to plan a short, efficient visit that maximizes technical takeaways and networking opportunities.
MyHDL Resources and Projects
Christopher Felton has pulled together a compact, practical guide to learning and using MyHDL, with the essential manual, Jan Decaluwe's deep dives, presentations, example projects, and active Git/Bitbucket repos. Whether you want a tutorial path, reference reads, or hands-on FPGA projects from simple LEDs to SDR and DSP cores, this curated list points you to vetted resources and real designs to study and reuse.
Feedback Controllers - Making Hardware with Firmware. Part 2. Ideal Model Examples
An engineer's guide to building ideal continuous-time models for hardware emulation, using TINA Spice, MATLAB and Simulink to validate controller and circuit behavior. The article shows how a passive R-C network can be emulated by an amplifier, a current measurement and a summer, with Spice, MATLAB and Simulink producing coincident Bode responses. Small phase differences between MATLAB and Simulink are noted, and sampled-data issues are slated for the next installment.
ESC Boston's Videos are Now Up
In my last blog, I told you about my experience at ESC Boston and the few videos that I was planning to produce and publish. Here they are, please have a look and any feedback (positive or negative) is appreciated.
Short HighlightThis is a very short (one minute) montage of some of the footage that I shot at the show & conference. In future shows, I absolutely need to insert clips here and there of engineers saying a few words about the conference (why they...
Feedback Controllers - Making Hardware with Firmware. Part 6. Self-Calibration Related.
This article will consider the engineering of a self-calibration & self-test capability to enable the project hardware to be configured and its basic performance evaluated and verified, ready for the development of the low-latency controller DSP firmware and closed-loop applications. Performance specifications will be documented in due course, on the project website here.
- Part 6: Self-Calibration, Measurements and Signalling (this part)
- Part 5:
Elliptic Curve Cryptography - Key Exchange and Signatures
Elliptic curve mathematics over finite fields helps solve the problem of exchanging secret keys for encrypted messages as well as proving a specific person signed a particular document. This article goes over simple algorithms for key exchange and digital signature using elliptic curve mathematics. These methods are the essence of elliptic curve cryptography (ECC) used in applications such as SSH, TLS and HTTPS.
