Retro Modules

This release includes a minor update to din5-270 & din-8. The changes are described in the release notes.

The extensive documentation updates mentioned in the recent Retro Modules for Education project log have been merged! These documentation updates will help ease use of Retro Modules significantly. Here are a few pages that have been overhauled:

• DA-15
• DB-25
• DE-9

Note that each numbered contact links to one or more pages that further explain the capabilities of the contact.

As the first of the prototype PCB's started rolling in, it became clear that some minor tweaks were needed to help keep things super-simple. The prototype boards are very encouraging! More on that soon! The proposed changes optimize the most commonly used connectors in the specification to reduce the need for numerous voltage regulators & further refine clean signal support.

* Adds dedicated common bus for digital signals on many connectors.
* Revises main connectors to support 6 & 40 volts max contacts.
* Adds support for balanced audio on main 25 contact connectors.

That last item is super-important. More & more dev boards feature analog audio playback capabilities, but the audio is typically rather noisy. Even analog audio from a higher-quality source is often negatively affected by nearby digital signals. Ideally a broadcast-quality digital audio protocol should be used, such as AES (or a board-to-board protocol like I2S). Unfortunately, the flat modular topology of Retro Modules does not support those signals (two boards emitting I2S on a shared bus is a big problem). A suitable work-around is to use balanced line-level analog audio signal, which is used by audio professionals worldwide. Balanced audio DAC boards (and amps supporting balanced audio) are readily available & inexpensive.

Here's the proposed update!

There aren't that many revisions, thankfully. Lots of new additions, but not too many changes from Version 1.0. Most protocols used by Retro Modules work well without any sort of router managing traffic. These few proposed changes are to help increase the probability of Retro Modules working well together.

Modules using DE-9 or 2x5 headers can now easily request power by connecting one of the contacts to common. Previously this functionality could only be found on larger connectors.

Audio-related modules can now utilize up to four line-level contacts. Two channels could be used for music & two for experiments. Two channels could be used for sending audio & the other two for returning processed audio (e.g. an audio effects processor module with stereo aux send & return).

There are a few new header specifications, such as a 4x4 palindromic header & a 3-contact keyed power connector with 1-Wire Data (for temperature sensors, etc).

This proposal will be merged in about 30 days as-is if there are no objections. Stay tuned! Printed PCB's in the works...

This is it! While not exactly ground-breaking news... it is newsworthy!

The 1.0 spec is a culmination of intermittent experimentation since the genesis of the project in 2015. It includes support for up to 400 watts via the average DB-25 connector, along with support for various common communication protocols -- both legacy and cutting-edge. Stability has been the goal, and now it is here for the most common connectors in the specification. Contacts have been optimized to reduce signal interference, separate high voltage supplies from low-voltage logic & to generally make design/assembly easier. These connectors support tiny, efficient low-voltage modules & big power modules alike!

Now that the spec is stable, large-scale production runs are on the horizon. Stay tuned!

It's right here!

This release is pretty significant. I am preparing to shift from the oft-repeated arduous process of hand-soldering modules... to creating printed circuit boards. I wanted to have the specs for the major connectors (DE-9, DA-15, DB-25, etc.) firm before moving forward with any production runs.

The key things that have changed:

• DA-15 is now an Enhanced Battery Connector.
  • LiPo batteries already have a balance connector. Why use an EBC instead?
    • Pretty much all balance connectors in the RC industry merely allow a battery charger to monitor two or more cells of a battery pack with an unknown chemical composition. The EBC spec supports battery packs with 6 cells (e.g. 6S) & includes one id pin. This pin has a resistor connected which can be used to identify both how many cells are in the pack, and what their chemical composition is. For instance, a 4S LiPo could have a simple 1.3Kohm resistor embedded within. Off-the-shelf battery chargers could include new functionality that analyzes the resistor value of the battery pack, compares it to the matrix & pre-loads the best settings for charging the pack.
  • LiPo batteries are already too heavy. Why add a heavy old-school DA-15 connector?
    • You don't have to! You can use a 16 contact socket IDC header instead. All 16 contacts are only really necessary on a fully-equipped 6S battery pack. A 3S pack would still use the 16 contact socket IDC header, but could terminate as few as four wires on said header.
  • Why not smaller?
    • There's nothing that would prevent use of a smaller connector. It seems, however, that good-ol' 2.54mm headers are best suited for external battery management, and 16 contacts seems to provide just enough functionality & flexibility.
  • Why no digital communication?
    • There is! I was able to squeeze in `one-wire-data` on contact 1. This digital bus allows one to embed inexpensive digital temperature sensors & similar into the pack.
  • Why support only LiPo?
    • They support more! Enhanced Battery Connectors support Pb (lead acid), NiMH, LiIo & LiFe batteries as well! As seen on the matrix.
• DC-37 is now 'The High-Def D-Sub'.
  • The connector now is spec'd to support HDBaseT (1080, 4K, etc), USB3, & standard BaseT connections. Example: "6x Raspi's and/or 6x Nvidia Jetsons sharing a backplane."
• Most connectors now support up to 40VDC.
  • Why so high?
    1. 24V battery systems (such as those in some RVs) may reach voltages as high as 36V while charging. I wanted Retro Modules to be compatible.
    2. A grid of 9x 18650's (a 3x3 9S battery pack) has a max safe voltage of 37.8VDC.
    3. While the average D-Sub contact can support up to 5A, D-Subs with IDC termination use wires that can only support about 1.2A each. An increase in the maximum supported voltage safely allows for more wattage on those same wires.
    4. Some module arrangements may have a common backplane, while some module arrangements may feature daisy-chaining. The higher voltage allowance helps reduce risk of connection-related power delivery issues.
  • Why not higher?
    1. 40VDC is the maximum voltage supported by many inexpensive DC-DC buck converters that use the LM2596 (or similar) regulator.
    2. Voltages over 50V can be considered dangerous (hat tip to: @Njkotzur via https://hackaday.io/project/45999-dewalt-flexvolt-60v-battery-adapter/discussion-100764)
• Many connectors now support (on a dedicated contact) voltages up to 15VDC.
  • Why up to 15VDC?
    1. Smaller modules may not have any room for a beefy DC-DC buck converter. The lower voltage limit allows for simple linear regulators (etc) if needed.
    2. Smaller modules may not need much power at all.
    3. Many 12VDC automotive accessories are able to tolerate up to 15VDC.
• Some connectors now support 12VDC with the ability to request more.
  • Why the complexity?
    • There are many 12VDC automotive accessories (and similar) that prefer just that: about 12VDC. The connectors (such as `din5-240`, `din6-240` & `din8`) will provide about 12VDC by default if a suitable power source is available. Some devices, however, make do with 12VDC -- but work better with higher voltages if they are available. These connectors (much like functionality described in USB-C PD documentation) are able to provide more power if a source can provide it & the client device requests it.

This spec is becoming easier & easier to work with. I'm now able to manually make one or two modules in an evening with great ease. I'll be posting a few new (related) projects soon!

Work is continuing in earnest for the 1.0 spec release. This spec release is expected to be firm & as such, an audit of many connectors has been performed. The proposed changes include new flexibility on the power-related contacts & optimizations to reduce interference.

There have been some exciting developments concerning multi-cell battery support, as well as support for some more exotic modules. Looking forward to sharing more with you soon!

This latest pull request introduces a few modules (and 3D-printable files) designed to solve power-related issues. One of the main concerns I've had over the past several months was how readily-available power supplies & batteries might fit into the specification. One of the goals of the specification is to encourage adopters to use parts they already have in their shop. Power tool batteries, for instance.

Presently, most connectors noted in the spec at http://retrospec.cc have pins which can accommodate up to 20VDC. Most power tool batteries have a nominal voltage of around 18VDC, but can exceed 20VDC at full charge. For these types of batteries to be used, the average max power rating for connector pins needed to be higher. How high, though? An RC-industry 6S LiPo battery can exceed 25V at max-rated charge. Most golf cart batteries (and newer fancy RV batteries) have a 24VDC nominal voltage. In the end, I decided to go with 30VDC max voltage on most pins in the new proposal. Many inexpensive DC-DC buck voltage regulators are rated to work with voltages up to 30VDC. These regulators can easily fit into most modules, run efficient & run cool. This higher voltage allowance permits more power-hungry modules on the same relatively thin wires.

The new pull request (http://retrospec.cc/new) includes STL files for the two leading power tool manufacturers & reference information. Files for other leading power tool manufacturers will become available within the coming months. Support for LiPo batteries of varying form factors will follow. For lower-power projects, the good ol' 9V Battery module will certainly suffice.

The larger batteries presented a new opportunity for a standardized modular footprint. After messing around with a few different approaches I settled on the idea that one should be able to just print (or CNC/laser) thin plates... or full enclosures. The hole pattern accommodates up to 2X DA connectors, up to 2X DB connectors, up to 2X DC connectors & up to 4x DE connectors. These connectors, when mounted, should ideally be arranged in a palindromic fashion for greater ease of use.

All power-supplying modules using this footprint should have all female connectors. Each pin on a typical D-Sub connector can accommodate about 5A. As such, resistor-style fuses (or auto-resetting fuses) should be between each power pin and the actual power source. The connectors should ideally have all contacts properly connected so a small module plugged in on one side of the footprint can talk to a small module on the other side. If you're in a rush... just wire up the power contacts. You can always come back later & upgrade.

The footprint will allow for all sorts of small-form-factor computing devices to run atop a power tool battery. The new pull request includes STL files for Raspberry Pi devices & full-size Arduino devices... with support for more devices coming soon. Each of the holes in the STL file designs are compatible with M3 screws or Imperial #6 screws. Screws & standoffs can be purchased at many PC or RC part supply stores.
Since there are 2X 30VDC pins on DB-25 connectors & 1X 30VDC pins on DE-9 connectors, the configuration shown above can accommodate up to 30VDC at up to 30A. Please make sure to check the new PR (again at http://retrospec.cc/new) for new pin specs for high-current D-Sub connectors (with some accommodating up to 60VDC at up to 80A & some soon which will accommodate 60VDC at up to 160A).

This PR is a big bold step for this little free modular framework.

Putting the finishing touches on a new pull request. This one is going to be fun. The dust is settling. Some of the big blockers are being resolved.

Stay tuned. New post next week.

This pull request sums up several months of occasional planning & research work. The projects listed are projects that interest me; projects that I intend to build and/or contribute to in the future. Given present time constraints, I've simply chosen to compile notes about each project in the repo with the hope that others might find the reference material useful -- and that I can reference that material when I'm ready to do some serious building again.

The general idea of the repository is to provide a common electrical specification for maker-friendly projects. Adding known modular projects into the mix helps provide some extra inspiration. Modules & modular project reference materials are expected to be the complete scope of the repository.

More to come!

Pull Request 10

Instagram

Just finished up editing module ideas I've been dwelling on since February. Since the specification is now fairly stable, the focus now is: what can be built? Many big custom builds are just that: big & custom. Once demoed... they may be purposefully destroyed or fall into disrepair. With a basic open spec, modular parts of a big build can be salvaged & saved for later. Most of the ideas in this latest proposal are bigger ideas -- broken up. I'm looking forward to building a bunch of these. Since I do not (nor will ever have) the time to build all the things, I have included many references to other components & in some cases, other projects.

http://retrospec.cc/proposed/client-modules

http://retrospec.cc/new