EXT Cartridge Module

Hi, am I to late to get one too?

Not at all, the thing is that mostly I am a coward and didn’t release yet.

That’s not good, so let me make it up to all and finally do it.
Tough I must stress that I consider it unfinished because the fan support is basically none as of yet and the main daemon and printer software is only tested on A06, instruction manuals won’t be included and I hope I can give all the support needed in this thread.

I calculated the component costs and it’s totaling 37.07€, I’m willing to give it away at 40€ as I consider it not a complete product.

Detailed breakdown

I got only 5 pieces soldered up completely, which was a pain to do and I won’t do any more.
The main reason is that I chose the wrong TVS diodes for input protection of which there are 17 per board, and it takes 5-15 minutes to solder one as the pads aren’t designed for hand soldering.
Give me one more month give or take and I’ll have all the things (EXT, printer kit, USB kit, Ethernet & RS232 module, breakout board kit) listed on Tindie.

Currently, only the 5 EXTs and 8 Ethernet/RS232 cartridges are ready.
I need to work a bit on the printer case as it’s not stable enough.
Also all the cases for the breakout board cartridge have yet to be printed.

TL;DR sorry for neglecting this project, give me a month or so to get into it again and I’ll release it


So what would be the price for everything?

And maybe I can help with the printer driver.
I shared a updated printer driver some days ago here that should work with new releases of wiringpi. I only tested it on cm4 yet, because I only have cm4.
But maybe, if your printer modules spi is accessible via /dev/spidev, i could make a version of my driver, that should work with your printer module

I calculated the price for everything, it’ll be 40€ for the EXT, and with all the accessories it’s totaling to 142€. That’s the absolute cheapest I can give those away for. I don’t know how to feel about labor put in, if it’s okay I’ll bump up the baseline prices by a few euros.

Ethernet and RS232: 50€
Components Ethernet+RS232
Item Amount Bulk Price/EUR Unit Price/EUR Amount Component Price
Populated PCB 10 299.82 29.982 1 29.982
RJ45 Ethernet 16 56.16 3.51 2 7.02
RJ45 Serial 8 44.8 5.6 1 5.6
Printed Case 1 2 2 1 2
Sum Per Unit 44.602 EUR

Let’s just round this to 50€.

Printer Kit: 20€
Components Printer Kit
Item Amount Bulk Price/EUR Unit Price/EUR Amount Component Price
Populated PCB 10 146.82 14.681999999999999 1 14.681999999999999
Printed Case 1 2 2 1 2
Sum Per Unit 16.682 EUR
Let’s say 20€.
USB Kit: 12€
Components USB Kit
Item Amount Bulk Price/EUR Unit Price/EUR Amount Component Price
Bare PCB 10 69.95 6.995 1 6.995
USB Sockets 30 32.7 1.09 3 3.2700000000000005
Sum Per Unit 10.265 EUR
12€ is a nice number, let’s say that.
Breakout Board: 20€
Components Breakout Board
Item Amount Bulk Price/EUR Unit Price/EUR Amount Component Price
Bare PCB 10 16.75 1.675 1 1.675
Pinheader 22x1 20 25 1.25 2 2.5
Socket 44pin Expander 5 34.65 6.93 1 6.93
Socket 44pin Cartridge 12 9.75 0.8125 1 0.8125
Cable 10 24.8 2.48 0.82 2.0336
IDC Socket 10 21.9 2.19 2 4.38
Printed Case 1 1.5 1.5 1 1.5
Sum Per Unit 19.8311 EUR

Rounded up it’s 20€.

About the printer driver, it works without any problems but it’s messy code.
You can find the code here.
To clarify, the kit for the printer needs your stock DevTerm thermal printer module,
so it’s basically the same code apart from using a different I2C ADC for temperature sensing.

Then sadly i can only afford the ext and printer module for now, and only in one or two months…

This looks like an interesting module and I would definitely like to buy one once you’re ready

Thanks for sticking with me. I think it’s time for another update.

The network+serial and the breakout carts are ready, and the printer cartridge cases are currently printing.

However I made a mistake while soldering the extension boards, which was revealed as this nasty white crud once I washed them with alcohol. Apparently this is a sign I was soldering too hot.

I am currently waiting on a professional PCB cleaner to arrive in the mail and hoping that this will clean it up.

Here’s a view of my unit, the battery holder now has a sticker to prevent shorts from its screws.
Don’t worry about the cable colors, the polarity of the board socket is reversed.

The fans I ordered tough have an absurdly long cable, I can either bunch them up like this or cut+solder them, I think I’ll go with shortening them.

Again, thank you for your patience.
I had a lot going on the last couple of months, but I am glad I am back on track on delivering this.
It also has been quite the learning experience for me regarding manufacturing of a product.


I’ve been away from this community for a while, its awesome to see you are not only still going with this but actually close to it being a real, tangible thing!

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since my original ext board seems to be toast I am interested in this module. I’d be willing and able to get the full set of cartridges as well. I am using an R-01 module though (I may be able to sort out any issues with that).

Good, but keep in mind that the printer cartridge kit needs the stock printhead because I couldn’t source this part for the life of me. Yours seems too far gone I’m afraid.

Another update while I’m at it, the EXT modules are all assembled, cleaned with no more residue, and now need to be tested. A short manual will be included as well for the EXT, printer and USB kits.

Tasks to be done are the following, in order of priority:

  • testing of the EXT modules themselves by checking the USB ports, scanning the I2C bus and printing a test page
  • print the last batch of printer cart cases again because I ran out of filament
  • writing the manual for the printer kit, the assembly can be a bit tricky

One more weekend should do it if testing goes well, two more weeks if I run into some last-minute troubles, hoping for the best :crossed_fingers:

I will burn that bridge when I cross it (-: I wouldn’t want to burn yet another ext board with it.

It’s been 16d since my last update, I think I am overdue for some explaining.
TL;DR: I am waiting on Tindie to approve all my listings.

That’s about it, all the stuff has been tested, manuals are printed and packing material is ready.
I am waiting on all products to be public and finally post here before I enter stock.
That way everyone has an equal chance to get one.

Recently, the Openterface Mini-KVM caught my attention and the first thing I thought when I realized this was fully open is stealing their homework and designing a KVM cartridge for this system.
I for sure would get good use out of that, and I feel like I am not alone with that notion.
Tough there’s still quite a bit to do for the software side, unless I’m told otherwise I won’t procrastinate with another project.

Bumping again for an unfortunate update, after a really long time not using my LimeSDR cartridge I now noticed that the TVS diodes cause trouble with some (could be even the majority) of USB devices. With these soldered, some devices as this SDR don’t seem to enumerate with an errno 71. I’m at a crossroads now, I invested a very long time to solder these, because having no input protection is not acceptable. If I desolder them, well, the USB hub could get damaged by static discharges, which is also unacceptable, but less so in my opinion.
The diode is SDD32C05L01 by YAEGO for the interested.

My plan forward is that I’ll list all of my stock as prototypes in the fleamarket section of Tindie with the TVS diodes removed from all USB data lines, with a hefty discount of course.
There will be however a second batch later this year, and that one will fix several issues mainly with production, but also this issue.

I guess I got fooled by the self-tests, as plugging in a CH341 USB UART worked just fine.
Sorry for the disappointment, this whole batch is cursed :unamused:

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