Scorchers, Part 4: Burned by the Happy Path (Simon Says)
Designs that only work along the happy path break in real use, causing frustration and sometimes safety risks. Jason M. Sachs uses everyday examples from microwaves to car Auto Park logic to show how mutable software and physical state create brittle behavior. He outlines practical firmware fixes such as clear state machines, sensor or user-driven resynchronization, soft-start delays, and a ‘‘Drunken Happy Path’’ fuzzing approach to find real-world failure modes.
Lost Secrets of the H-Bridge, Part V: Gate Drives for Dummies
Learn the most important issues in power MOSFET and IGBT gate drives: - Transistor behavior during switching - Calculating turn-on and turn-off times - Passive components used between gate drive IC and transistor - Reverse recovery - Capacitively-coupled spurious turn-on - Factors that influence a good choice of turn-on and turn-off times - Gate drive supply voltage management - Bootstrap gate drives - Design issues impacting reliability
Turn It On Again: Modeling Power MOSFET Turn-On Dependence on Source Inductance
This is a short article explaining how to analyze part of the behavior of a power MOSFET during turn-on, and how it is influenced by the parasitic inductance at the source terminal. The brief qualitative reason that source inductance is undesirable is that it uses up voltage when current starts increasing during turn-on (remember, V = L dI/dt), voltage that would otherwise be available to turn the transistor on faster. But I want to show a quantitative approximation to understand the impact of additional source inductance, and I want to compare it to the effects of extra inductance at the gate or drain.
Linear Feedback Shift Registers for the Uninitiated
Jason Sachs assembled an eighteen-part deep dive into linear feedback shift registers, connecting the simple shift-register circuit to finite-field algebra and practical tools. The series walks through primitive polynomials, Berlekamp-Massey state recovery, libgf2-based analysis, discrete-log methods, and real-world uses from PRNGs and Gold codes to Reed-Solomon and CRC reverse-engineering. It’s a single reference for engineers who want both theory and working code.
Modeling Gate Drive Diodes
This is a short article about how to analyze the diode in some gate drive circuits when figuring out turn-off characteristics --- specifically, determining the relationship between gate drive current and gate voltage during turn-off of a power transistor.
Ten Little Algorithms, Part 7: Continued Fraction Approximation
In this article we explore the use of continued fractions to approximate any particular real number, with practical applications.
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 5)
Most of the time a wafer spends in a fab is spent waiting in queues, not being processed. Jason Sachs peels back why cycle times stretch weeks to months, covering WIP accounting, die and wafer banks, the days per mask layer metric, and how variability and utilization tradeoffs turned fab behavior into a major factor in the 2021 chip shortage.
Return of the Delta-Sigma Modulators, Part 1: Modulation
Jason Sachs returns to delta-sigma modulators with a hands-on, code-first treatment that focuses on the DAC side of things. Part 1 walks through first- and second-order kernels, linearized analysis, spectra, and practical coefficient choices while illustrating results with Python simulations. Expect clear rules of thumb for A, R, and B, a derivation of noise shaping behavior, and a useful error bound for RC filtering.
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 4)
The chip shortage didn't end with 2021, it moved into older process nodes where cars and industrial gear live. In this installment Jason Sachs explains why mature-node and trailing-edge capacity remain tightly constrained, how NCNR commitments and price increases are reshaping supplier behavior, and what companies like NXP and Microchip are doing to cope. He warns the imbalance could take multiple semiconductor cycles to fix.
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 3)
Jason Sachs pulls back the curtain on Moore's Law and the foundry business to explain why the semiconductor shortage exposed brittle economics. He traces how roadmaps, depreciation schedules, and node mix force foundries to juggle expensive new fabs and mature capacity, and shows why leading-edge nodes punch above their volume share in revenue. Engineers get practical insight into how capacity and timing decisions ripple through the supply chain.
Important Programming Concepts (Even on Embedded Systems) Part I: Idempotence
Idempotence is a simple design principle that prevents duplicate effects when operations are retried or repeated. Jason Sachs shows why it matters in embedded systems, from HTTP submit buttons and capacitive touch inputs to garage-door remotes and SPI DAC writes. Read this post to learn three practical idempotent techniques and when redundant writes are a sensible reliability trade-off.
Development of the MOS Technology 6502: A Historical Perspective
A tiny team at MOS Technology pulled off one of the most influential microprocessor wins of the 1970s, creating the 6502 by marrying clever circuit choices with pragmatic manufacturing techniques. This excerpt by Jason Sachs focuses on the NMOS depletion-load process, mask and layout workflows, and yield-improving tricks like Micralign projection lithography and spot-knocking, showing how engineering and process decisions made a low-cost CPU ubiquitous.
How to Read a Power MOSFET Datasheet
Jason Sachs takes a soapbox to stop a recurring mistake: misreading power MOSFET datasheets. This practical guide separates marketing blurbs and typical graphs from the specifications you can actually rely on, and explains how to use RDS(on), VGS, gate charge, SOA and thermal data in real designs. Read this before you pick a MOSFET or size a gate driver.
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 4)
The chip shortage didn't end with 2021, it moved into older process nodes where cars and industrial gear live. In this installment Jason Sachs explains why mature-node and trailing-edge capacity remain tightly constrained, how NCNR commitments and price increases are reshaping supplier behavior, and what companies like NXP and Microchip are doing to cope. He warns the imbalance could take multiple semiconductor cycles to fix.
Linear Feedback Shift Registers for the Uninitiated, Part V: Difficult Discrete Logarithms and Pollard's Kangaroo Method
Most discrete-log problems are hopeless by brute force, but clever algorithms cut that cost to feasible levels. This installment walks through baby-step giant-step, Pollard’s rho and kangaroo methods, and how Silver-Pohlig-Hellman and index calculus leverage group structure to speed attacks on GF(2^n) fields. Jason Sachs includes Python examples, heuristics, and complexity nuggets so you can see when each method is practical.
Lost Secrets of the H-Bridge, Part IV: DC Link Decoupling and Why Electrolytic Capacitors Are Not Enough
Switching H-bridges can kick nasty voltage spikes onto the DC link, and a single electrolytic capacitor rarely fixes the problem. Jason Sachs uses simulations and practical PCB layout advice to show how a three-tier decoupling strategy — bulk electrolytic, mid-value ceramics or film, and many small HF bypass capacitors plus PCB plane capacitance — tames spikes, reduces EMI, and avoids harmful resonances when parts and vias are placed correctly.
Return of the Delta-Sigma Modulators, Part 1: Modulation
Jason Sachs returns to delta-sigma modulators with a hands-on, code-first treatment that focuses on the DAC side of things. Part 1 walks through first- and second-order kernels, linearized analysis, spectra, and practical coefficient choices while illustrating results with Python simulations. Expect clear rules of thumb for A, R, and B, a derivation of noise shaping behavior, and a useful error bound for RC filtering.
Tolerance Analysis
Jason Sachs walks through practical tolerance analysis by designing a 24V overvoltage detector from the ground up, combining resistor tolerances, temperature coefficients, reference and comparator errors, hysteresis, and dynamic RC behavior. He demonstrates worst-case stacking with real datasheet numbers, shows how solder and mechanical stress affect resistor choice, and sizes filtering so the comparator meets a microsecond-range trip requirement. The article is a hands-on guide full of worked examples and trade-offs for embedded hardware engineers.
Linear Feedback Shift Registers for the Uninitiated, Part XVI: Reed-Solomon Error Correction
Jason Sachs demystifies Reed-Solomon codes with hands-on examples and pragmatic tips for embedded engineers. The article shows why RS encoding is just polynomial division in GF(2^m), why decoding is mathematically heavier, and how to implement encoders in Python and in C-friendly form using LFSRs and table-driven methods. Read this for working code, generator-polynomial examples, and an embedded-minded view of RS practicalities.
Important Programming Concepts (Even on Embedded Systems) Part V: State Machines
State machines are not glamorous, but they solve a lot of real embedded problems. Jason Sachs uses a motorized couch example to show how FSMs and Harel statecharts expose corner cases, simplify timing constraints, and make behavior easier to specify and review. The article walks through hand-rolled switches, tabular implementations, the state pattern, libraries like QP and Boost, and tool tradeoffs.
Development of the MOS Technology 6502: A Historical Perspective
A tiny team at MOS Technology pulled off one of the most influential microprocessor wins of the 1970s, creating the 6502 by marrying clever circuit choices with pragmatic manufacturing techniques. This excerpt by Jason Sachs focuses on the NMOS depletion-load process, mask and layout workflows, and yield-improving tricks like Micralign projection lithography and spot-knocking, showing how engineering and process decisions made a low-cost CPU ubiquitous.
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 2)
Jason Sachs zooms through semiconductor history, fab economics, and the microcomputer era to explain why the 2021 chip shortage unfolded the way it did. He blends technical explainers on photolithography, yields, and node migration with business lessons about risky multi-year fab investments and cyclic demand. Engineers get historical case studies and practical signals to watch when designing products for greater supply resilience.
Analog-to-Digital Confusion: Pitfalls of Driving an ADC
Wayne's thermistor board showed one ADC channel changing when another was heated, a classic case of ADC input cross-coupling. The post walks through how multiplexed ADCs, the small sample-and-hold capacitor, source impedance, sampling time, repeated sampling rates, and added charge reservoirs interact to create errors. Learn practical fixes including increasing sample time, sizing external caps, adding op-amp buffers, and using an RC dampener with PCB layout tips.
Help, My Serial Data Has Been Framed: How To Handle Packets When All You Have Are Streams
Framing byte streams is easier to get wrong than you think, and a bad scheme can leave your embedded device acting on the wrong packet. Jason Sachs walks through common plaintext and binary framing approaches, explains why CRCs alone can still permit false resynchronization, and demonstrates COBS as a simple, low-overhead byte-stuffing method that prevents delimiter collisions and guarantees resynchronization.
10 Software Tools You Should Know
Embedded work gets a lot easier when you have the right software stack, and Jason Sachs lays out the tools he leans on every day. From revision control and file comparison to build systems, scripting, analysis, documentation, QA, and command-line utilities, he focuses on practical picks that save time and reduce mistakes. The list is opinionated, but it is full of the kind of workflow advice that helps engineers stay productive.
Byte and Switch (Part 1)
Driving a 24V electromagnet from a 3.3V microcontroller looks trivial, but Jason Sachs shows how that simple switch can fail spectacularly. He walks through the cause of MOSFET destruction when an inductive load is turned off, and explains the practical fixes you actually need: a flyback diode, a gate series resistor, and a gate pulldown to keep the transistor well behaved.
How to Build a Fixed-Point PI Controller That Just Works: Part I
Jason Sachs digs into the implementation choices that make a fixed-point PI controller reliable in real embedded systems. He focuses on practical fixes rather than tuning: prefer scale-then-integrate, fold the timestep into the integral gain, and apply anti-windup so saturations and sensor noise do not break the loop. Part I covers discrete-time pitfalls and sets up fixed-point scaling issues for Part II.
Important Programming Concepts (Even on Embedded Systems) Part V: State Machines
State machines are not glamorous, but they solve a lot of real embedded problems. Jason Sachs uses a motorized couch example to show how FSMs and Harel statecharts expose corner cases, simplify timing constraints, and make behavior easier to specify and review. The article walks through hand-rolled switches, tabular implementations, the state pattern, libraries like QP and Boost, and tool tradeoffs.
Supply Chain Games: What Have We Learned From the Great Semiconductor Shortage of 2021? (Part 3)
Jason Sachs pulls back the curtain on Moore's Law and the foundry business to explain why the semiconductor shortage exposed brittle economics. He traces how roadmaps, depreciation schedules, and node mix force foundries to juggle expensive new fabs and mature capacity, and shows why leading-edge nodes punch above their volume share in revenue. Engineers get practical insight into how capacity and timing decisions ripple through the supply chain.
Lost Secrets of the H-Bridge, Part V: Gate Drives for Dummies
Learn the most important issues in power MOSFET and IGBT gate drives: - Transistor behavior during switching - Calculating turn-on and turn-off times - Passive components used between gate drive IC and transistor - Reverse recovery - Capacitively-coupled spurious turn-on - Factors that influence a good choice of turn-on and turn-off times - Gate drive supply voltage management - Bootstrap gate drives - Design issues impacting reliability
