The Amp Hour · 16 May 2022 · 1h 05m · Episode 589
Dave Jones and Chris Camel discuss the quirks of online circuit simulators like Falstad and LTSpice, specifically the confusing use of 'beta' for MOSFETs. They analyze Derek Muller's (Veritasium) follow-up video on energy flow in transmission lines, debating Poynting's theorem versus the lumped element model. The conversation shifts to embedded systems debugging with SEGGER tools, the ongoing microcontroller supply chain crisis, and the challenges of adopting open-source solar microinverters.
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Elecia White and Christopher White discuss Elecia's recent burnout while teaching her Making Embedded Systems course on Classpert, and Christopher's debugging of a subtle SPI + FreeRTOS bug on a Cypress PSoC chip. They also cover Elecia's recommendations for the book 'Thanks for the Feedback', the Wokwi simulator for Raspberry Pi Pico, and listener projects like Serial Wombat and Cyanobyte.
Hosts Carl and Corey revisit topics from their first 31 episodes, discussing the NXP acquisition of Freescale, MakerBot's layoffs, and Tesla's certified pre-owned program and Powerwall. They also analyze the John Deere firmware ownership controversy, the performance trade-offs of No-OS and Lua on microcontrollers, and the evolution of the Raspberry Pi. The episode highlights specific components like NXP current-sensing MOSFETs and the PCA8550 I2C dip switch, while addressing software bugs in Boeing 787 generator control units and the importance of checking simple parts like LDOs.
Mike Engelhardt, creator of LTspice and now QSPICE at Qorvo, explains how he built circuit simulation tools starting from his work in physics labs and oil exploration. He details the rapid development of LTspice in 10 months to serve as sales collateral for Linear Technology, emphasizing that simulation's primary value is building engineer intuition rather than just verification. Engelhardt then describes refactoring the open-source Berkeley SPICE code to create QSPICE, which fixes bugs in the sparse matrix package and leverages GPUs for waveform plotting rather than computation to handle wide bandgap semiconductors like GaN and SiC.
Hosts Carl and Corey discuss a grab bag of embedded electronics topics, starting with their new remote recording setup using Shure and MXL microphones. They review the TI ADS1263 32-bit ADC and the Lattice iCE40 FPGA ecosystem, highlighting the open-source Project Ice Storm toolchain. The hosts then critique the Raspberry Pi Zero's limited I/O and the safety issues surrounding lithium-ion batteries in 'hoverboards', before Corey airs a grievance about poor PCB differential pair routing practices.
Hosts Carl and Corey discuss the fragmented landscape of in-circuit programmers and debuggers for embedded systems, highlighting the pain of dealing with incompatible protocols like JTAG, SWD, and proprietary interfaces from vendors such as NXP, Microchip, and ST. They detail the high cost of commercial tools like the SEGGER J-Link and the risks of relying on bootloaders, citing a $58,000 loss by SparkFun on their MicroView Kickstarter due to a bootloader overwrite error. The hosts advocate for understanding memory maps and linker scripts, and suggest building custom programmers or using open-source tools like OpenOCD to gain deeper knowledge of microcontroller internals and avoid vendor lock-in.
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