Bald Engineer: Recent Episodes
None
- Slides PDF: Electrolytics are Ticking Time Bombs
- Bit Preserve: GitHub Repo with Vintage Computer Schematics in KiCad
- Bald Engineer’s Capacitor Video Playlist
- TRS 80 Model 100 Cap Replacement Spreadsheet (add a pitch column!)
Talk for Vintage Computer Festival Midwest #20 (2025).
Multi-layer ceramic capacitors (MLCCs) are so ubiquitous that you see them on almost every printed circuit board. Engineers and supply chain managers often ask whether polymer electrolytic capacitors can replace MLCCs. The replacement could be because of availability, or an application cannot tolerate the extreme capacitance loss with MLCC’s DC Bias Effect. This video demonstrates what happens when you replace MLCCs with Polymer Tantalum (KO-CAP) capacitors.
Experience comparing DIY and Turnkey PCB assembly with the Bald SENSE project. This journey started almost four years ago. Thanks to a collaboration with MacroFab, I am finally collecting valuable environmental data with my custom Feather Wing.
A big thank you to MacroFab for manufacturing the boards and sponsoring the video. I also want to thank Unexpected Maker for their noteworthy contribution to the FeatherS3 microcontroller boards, which played an essential role in the video.
This video covers:
– The detailed design process of the sensor Feather Wing.
– My DIY assembly struggles and the rework that followed.
– Turning to MacroFab’s TurnKey assembly services to get the job done right.
– What I discovered about my garden with the help of this project.
For more information, check out this Bald SENSE post on AddOhms.
I dive into Pico Technology’s latest PicoScope oscilloscope software, PicoScope 7. Using a PicoScope 2000A (from the element14 Community), James walks through key measurements and demonstrations using the built-in arbitrary waveform generator. He explores new functionalities in PicoScope 7, such as the improved UI, a unique feature called DeepMeasure, and decoding I3C traffic.
I have been using the Pico Technology PicoScope 2000A for years. (Here is my older review!) It is an entry-level oscilloscope with 10 MHz bandwidth, 100 megasamples per second sample rate, and 8 kilosample of acquisition memory. Since it is USB-based, it has companion software running on Windows, macOS, and Linux.
PicoScope 7 introduces a significant visual overhaul. It features a highly flexible waveform display area, intuitive control boxes for timebase and trigger systems, and a left panel that holds channels and various functions. Users can customize the panel placement and quick-access buttons for enhanced workflow.
In this video, I demonstrate the software’s features using the 2000A’s built-in arbitrary waveform generator (AWG) to create a 1 kHz sine wave and other digital patterns. The DeepMeasure function, which provides detailed cycle-by-cycle analysis, stands out as a unique capability for in-depth measurement.
A highlight of the video demo is the I3C measurement, where I capture and decode I3C traffic using PicoScope’s free serial decoders. I then use reference waveforms to explain the differences between I2C and I3C protocols.
PicoScope 7 also includes advanced features like history mode, a detailed math editor, and FFT/Spectrum view, making it a versatile tool for engineers. The software is available for download even without hardware, allowing users to explore its features in demo mode.
Learn more on the e14 community
The Apple II’s ROM has the 8th bit set for all of its ASCII strings. This convention makes it difficult to search the ROM for hex strings quickly. This Python script takes an ASCII string and returns the HEX string with (and without) the 8th bit set.
Python Code
input_string = "Mega IIe"def string_to_hex_ascii(input_string, set_bit_8=False): hex_values = [] for char in input_string: # Get the ASCII value of the character ord() and convert it string # representing the hex() value # # [2:] strips the '0x' if (set_bit_8): hex_value = (hex(ord(char) | 0x80)).upper() # for Apple II, awww else: hex_value = (hex(ord(char))).upper() hex_values.append(hex_value[2:]) return hex_valuesdef print_list_with_spaces(input_list): # Join the list elements into a single string with spaces in between result = ' '.join(map(str, input_list)) print(result)def print_og_string_formatted(input_string): result = ' '.join(input_string) print(result)# Remind user of stringprint("Og : ", end='')print_og_string_formatted(input_string)# As-is ASCII in Hexhex_values_raw = string_to_hex_ascii(input_string)print("Raw : ", end='')print_list_with_spaces(hex_values_raw)# Hex with 8th bit sethex_values_8bit = string_to_hex_ascii(input_string, True)print("8bit: ", end='')print_list_with_spaces(hex_values_8bit)
Disclaimer: I used ChatGPT to generate an initial script for converting an ASCII string to a list of hex values. Then, I wrote the rest.
ExampleThe Apple IIe Enhanced ROM has the string Apple //e. It is displayed at the top of the screen during boot. Here is the 7-bit ASCII version and the 8-bit version found in the ROM file at address:
Og : A p p l e / / eRaw : 41 70 70 6C 65 20 2F 2F 658bit: C1 F0 F0 EC E5 A0 AF AF E5
Friday, June 21, 2024 @ 4:00 (PDT)Learn more about Teardown 2024Slides (Still in progress!)Links* Circuit Break Podcast #434: The Other VCC * Circuit Break Podcast #141: It Depends MLCCs with James Lewis * YouTube: Bald Engineer’s Capacitor Videos * Hioki USA: Unlocking the Secrets of Capacitor Impedance Plots * Murata: SimSurfing * Yageo Group / KEMET: K-SIM
The B&K Precision DAS60 is a data recorder. It features 6 wide-range voltage inputs, 16 digital channels, and RTD thermal sensor inputs and comes in a small compact form factor. In this video, I show what it can do.
The DAS60 is designed for lab and fieldwork. Its built-in battery means you can deploy it in a facility and let it log data. It has built-in ethernet and support for generic Wi-Fi dongles. The computer runs Windows CE and has RealVNC pre-installed. This combination lets you connect remotely to configure the instrument, check its status, or review recorded data.
See full post on the element14 Community
The Retro Repairs RoundUp crew invited me to be a guest on episode 56 of their livestream. As their name implies, they discuss retro computers and, in many streams, how to repair them. We mostly discussed the Mega IIe project. Sean was another guest who talked about KansasFest 2024.
KansasFest is an Apple II conference. This year, it moved its venue to Springfield, Illinois. The name and the location might seem confusing; however, it was long held in Missouri. So, it is a case of the name sticking for historical reasons.
It was great to be on the show, especially since I recognized everyone from other aspects of the retro community. You can watch the full Retro Repairs RoundUp here.
I must extend a big “Thank You!” to Lewin Day at Hackaday for this excellent Mega IIe write-up. Accompanying the post is an archived recording of my Supercon 2023 talk. That talk is where I gave a complete overview of the Mega IIe project and showed off the final case design for the first time! This project is where I took the Mega-II chip out of an Apple IIGS and built a fully compatible Apple IIe around it—something that not even Apple ever did!
Hackaday’s Superconference 2023 took place in Pasadena, CA. In addition to talking about the Mega IIe, I hung out with many great people from the electronics hardware community and saw many incredible talks.
You can download my slides from this resource page.
Check out NXP’s latest microcontroller boards. These boards of their new MCX-A and MCX-N microcontrollers. The form factor is what NXP calls Freedom (FRDM.)
The MCX line of microcontrollers, each with its unique set of features, caters to a wide range of projects. The MCX-A, a general-purpose microcontroller, is ideal for entry-level projects, while the high-performance MCX-N is designed for advanced AI/machine learning tasks. NXP recently started shipping the MCX-N, adding to its versatility and appeal.
The FRDM boards, with their various connection options, provide a high level of flexibility in design. NXP’s inclusion of an onboard simplifies the programming and debugging process, ensuring a smooth development experience. However, I did encounter some issues with the development environment.
The VS Code install was not smooth, and some of the examples from NXP’s Application Hub would not load. The Eclipse-based MCUXpresso fared slightly better, but it refused to program the MCX-N board for some reason.
With onboard debuggers, versatile connectivity options, and an affordable price range, these boards are an exciting option for any embedded designer.
See full post on the element14 community
I created a Wi-Fi-enabled LED Detector using Nordic’s nRF7002 Design Kit (DK). Using this box, I can detect when LEDs on appliances, like my lab’s dehumidifier, are on. In other words, my non-IoT tool can send me messages over the Internet now! And, because the nRF7002 has a dual-band Wi-Fi antenna, it does so on my 5 GHz network.
I ran into a number of issues with this project, and I expected that. Except for the RF part of the design, which works fine! Links to the design files are available on the post on the element14 Community.
April 17, 2024, at 1:00 pm CDTRegister NowCapacitors are deceptively complex devices. It is why I love talking about them so much! Hioki USA loaned me an LCR Meter that works as an Impedance Analyzer to try out some measurements. As a result, I noted a few things that might catch someone off guard if they have never attempted to characterize capacitors.
For example, many of us know about the MLCC DC Voltage Coefficient. However, do you know how to evaluate whether your parts lose 20 or 80% of their capacitance? Or, what considerations do you need to make when measuring a polymer electrolytic versus a film capacitor?
Another critical consideration: how do you connect an Impedance analyzer to a capacitor?!
These are all things I plan to cover. Sign up now to see the webinar.
Register Now!What You Will Learn* Overview of capacitor types: MLCCs, Electrolytics, and Polymers. * Understand the importance of characterizing capacitors. * Introduction to LCR/Impedance Analyzers: Understanding their role in measuring * capacitor parameters. * Equipment and Accessories for Capacitor Measurement: Key factors to consider. * Live Measurement Demonstrations: + Experience first-hand the do’s and don’ts of capacitor measurements through live examples that highlight common pitfalls and best practices.
Register Now!
The Apple II’s CPU clock has jitter or a glitch. This issue is not new—it has been present since its original design in 1977! Bald Engineer uses an oscilloscope to show how often the glitch occurs and how to correlate that jitter to its source—which is useful when you are not testing 40-year-old devices. The device under test (DUT) in this video is the Mega IIe project. It’s a fully compatible Apple IIe built around the Mega II chip.
Get related links here
A long time ago, I made a video suggesting math was unnecessary to determine proper pull-up resistor values. Like most generalized statements, that suggestion is not always true. For example, in data buses like I2C, speeds like 400 kHz and 1 MHz are common. At those speeds, the pull-up resistor and the bus capacitance form an RC filter that fundamentally limits the data transmission speed. Or. It limits the range of pull-up resistor values. In this Workbench Wednesdays video, I show how to estimate I2C bus capacitance, measure that capacitance, and pick pull-up resistor values.
Full Notes on element14 community
Parker and Stephen invited me back to discuss the Mega IIe project on the MacroFab Circuit Break podcast. This discussion was far more casual than my past appearances. It was the first time I didn’t feel the need to do any prep work for their excellent questions!
We talked through the overall experience of rev 1, rev 2, and rev 3. I appreciated the chance to talk about my motivations behind the Mega IIe project, why I like the Apple II platform so much, and getting to nerd out with Parker on analog video signal concepts.
Circuit Break Podcast #420
KiCad 8 just dropped. Here’s an AddOhms video covering eight must-try features! The February 2024 release brings a whole host of new stuff to the Schematic editor. However, the PCB editor, CLI, and Simulation tools also received attention. (There are something like 900 closed issues for the 8.0.0 Milestone!) Which of these is your favorite?
In the video, I cover:
- Property Manager Panel (is now everywhere)
- A fix for
Symbol pin or wire end off connection grid! - Easily access alternate pin functions (on symbols with them)
- Pin Helpers save time
- Edit Power Symbols (instead of creating new library parts)
- Net Navigator and Search panels help with large schematics
- Improved custom polygon tools in PCB
- (Combined) Teardrop support and Length-Tuning improvements
This AddOhms post covers my top 8 in more detail. Or, you could just watch the video!
USB-Based instruments that do not appear to the host as a virtual com port (VCP) usually use libusb for communication. The pyvisa-py driver for pyvisa can communicate with these instruments. However, you must first create a udev rule (and possibly a user group.)
If you see the device in lsusb, but not the pyvisa ResourceManager, you need to add (or modify a udev rule):
```
backup 99-com.rules (if it exists)cp /etc/udev/rules.d/99-com.rules /etc/udev/rules.d/99-com.rules.BAK# (create and) edit the filenano /etc/udev/rules.d/99-com.rules# Add the following lineSUBSYSTEM=="usb", MODE="0666", GROUP="usbusers"# create a usbusers groupsudo groupadd usbusers# add your account to the new groupsudo usermod -a -G usbusers USERNAME# restart udev/etc/init.d/udev restart(Although, you are probably better off rebooting.)
```
In August 2022, Nordic Semiconductor announced its first Wi-Fi product. The nRF7002 is a dual-band (2.4 and 5 GHz) Wi-Fi 6 compatible companion IC. It does not have a general-purpose microcontroller built-in. Instead, Nordic intends for you to combine it with another microcontroller, like one of their nRF52 or nRF53-series system on chip (SoC).
Nordic and the element14 Community sent me an nRF7002 Development Kit (DK), Evaluation Kit (EK), and some nRF7002 QFNs. I reviewed the nRF70 variants in this video and looked at the various boards. As the thumbnail suggests, I connected the Wi-FI transceiver to a FPC1500 spectrum analyzer.
You might be wondering what I am doing with the nRF7002 QFNs. Well, there is a big hint near the end of the video! You’ll have to watch it to see.
For more information, check out the post on the element 14 community.
During the component shortage, I got to know Raspberry Pi’s RP2040 microcontroller. It is a dual-core Arm Cortex-M0+ with about 262 kilobytes of RAM. The feature I like most is the programmable IO pins. These are small state machines that run independently of the Arm cores. They allow for some clever tricks. For example, I used them extensively on the Mega IIe project.
This video was supposed to be a project I thought of during the Mega IIe. I call it a state-mode logic analyzer. However, it took me several days to turn on and debug four boards. Time ran out, so I focused the video on debugging custom RP2040-based boards. These are all lessons I have learned from this project, plus about another dozen RP2040 boards I have built over the past couple of years.
Unlike a traditional logic analyzer, a state-mode logic analyzer only stores samples on a qualified clock edge. An example would be capturing 6502 bus traffic on the transitions of the PH0 clock. The advantage of this approach is you don’t need nearly as much memory to capture useful traffic.
I put together an idea for an RP2040-based state-mode logic analyzer to make a long story even longer. The PIO makes it possible to quickly capture all 32 bits of its GPIO pins and DMA that to RAM. That was the easy part. I added a 74LVC245 buffer to provide logic-level translation between the inputs and the RP2040. Then, I added a small counter circuit to create timestamps. Those timestamps are necessary to re-create how much time passed between captures.
The design files for the state-mode logic analyzer are available on GitHub. However, I have had to put the project down for now. I will pick this project up again in the future. However, my current plan is to use the existing boards as a prototype for an FPGA-based tool instead.
Another source for details is the How Hard Could It Be to Debug RP2040 boards post on the element14 Community.
Most of these pictures from the Mega IIe project did not make it into a video or talk. There were many “behind the scenes” style shots. Some of the pictures have titles and descriptions. I work on them when I have free time. Let me know your favorite!
Mega IIe Album on FlickrNavigate one picture at a time with the left/right arrows, or follow the link below to see the full album.
View Album on Flickr
Often I hear this question: “how can I get better solder joints?” Without looking at anything they are doing, I already know that they could be using more flux. Or, as I point out in this video, perhaps the correct type of flux! Flux removes oxide layers, gets contaminants out of the way, and makes [...]
A powerful, but an underused feature of digital oscilloscopes is the trigger circuit. Learn from James how to use an oscilloscope’s trigger to find glitches, measure pulse widths, see transients, and stabilize a scope’s screen. This video explains the difference between Auto and Normal sweep modes, shows how to use a Pulse Width trigger, and [...]
When running on a battery, it is important to know what parts of your circuit draw the most current. Profiling is a process where you look at sections of code or interactions with hardware to see how much power each requires. In this video, James shows four tools (and their tradeoffs) when profiling IoT or [...]
When connecting multiple oscilloscope probes to a circuit, does each probe need to connect to ground? The short answer is yes! Why? The long answer is kind because of the ground loop. Remember, a circuit needs a closed path. And while on DC circuits we may rarely think about the distance of that path, it [...]
Every digital oscilloscope I have ever used has a menu or dialog for “acquisition modes.” And depending on the current settings, changing that acquisition mode does not seem to have an effect on the signal. Or sometimes, changing to something like Average mode can completely destroy your measurements. It turns out, that the analog-to-digital converters [...]
Bench power supplies are an essential piece of test equipment gear. And like most test gear, they have a wide range of capabilities. For example, the B&K Precision 9140 is a triple output supply that can output up to 300 watts. But, the basic capability isn’t what interested me about the supply. Instead, it was [...]
In KiCad 6, using the Polygon tool makes square boards easy. Just select the Edge.Cuts layer, then the polygon tool, and draw a square. However, if you want custom shapes, then you need to connect multiple line segments together. If you are not careful, the segments will not connect and you might get one of [...]
Thank you again to those who came over from RSS to say the old feed was working. Also. My apologies for the rash of new posts. I thought I had a clever way to prevent them from appearing in the feed. Let me know if you see any issues. New (real) posts will start in [...]
Using a Metcal GT120, we look at three ways to improve your soldering skills. Using flux, setting a correct temperature, and selecting the proper tip all result in better solder joints. See how well the GT120 works while learning (or reviewing) some basics to improve your soldering skills. This episode was sponsored by Metcal.
Measuring a switch-mode power supply (SMPS) with a DMM might show a stable voltage. But the same DC rail on an oscilloscope can show a completely different story! In this video, learn how to correctly set up an oscilloscope to characterize the noise an SMPS creates in a circuit.