EXT Cartridge Module

Oh that’s smart, I got a Cisco serial cable around somewhere for RS45 to D-Sub.
Then 3 RJ-45s fit easily.

A switch to change the serial’s output level to CMOS/TTL/RS232 could fit, but would it be neccesary? Switching the output level would be nice but requires a level shifter, I don’t think the real estate on the board would accommodate this.

Still deliberating on either using an FTDI for RS-232 or using the DevTerm’s UART.
The case for the FTDI is that it’s truly plug and play through USB, for the DevTerm UART it’s less parts required but with additional configuration neccesary.

For the Ethernet chip I’m eyeing the LAN7850, tough soldering this one is going to be a challenge.
If anyone got a more accessible chip in mind, please do tell.

Sorry to break the bad news, but the cartridge system can only give out power,
not receive it and route it to the battery. Tough I got to admit, a power input module accepting low voltage AC or DC would be cool as hell.


Good news, I just assembled the revision 4 EXT module yesterday.
I’m still missing the GL850G USB hub tough, and the PWM fan controller and USB to UART I didn’t populate. Aside from that, it works very nicely!

Here’s the i2cdetect, all devices show up:

$ sudo i2cdetect -y -a 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --  <<-- 0x20: MCP23008 Port Expander
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --   <<-- 0x68: DS1307 RTC
70: -- -- -- -- -- -- 76 -- -- -- -- -- -- -- -- --   <<-- 0x76: BME280 via breakout cartridge

Regarding the edge connector position, @yatli hit the nail on its head, it fits perfectly with the parts I designed early on.

The only cartridge I can test right now is only the breakout adapter,
but that works as expected, added a BME280 to the I2C bus and it reads out as expected.

Parts for the thermal printer and camera module will arrive next week, then I’ll give an update on that when I got to testing.
Tough the mechanical aspect for the printer is sorted out now, just needed to adjust the model slightly.

Lastly, the LAN/RS232 combo module, routing is 87% done and I expect it to be finished in two to three months, giving myself a little leeway here because this one is packed.


I’d like to substitute a user module where the cell phone chip goes.

Time for the monthly update on the project.

The RS232/dual Ethernet cart came in, and it works nicely.
Did a few tests pinging and connecting RX to TX, no problems with either.
However the activity LEDs for the RS232 port don’t seem to work, but that’s not that important.

In other good news, the printer cartridge is confirmed working.

With the camera module I have a few troubles, I can’t seem to get the OV5647 working.
It does get initialized by the kernel, but got no usable video devices yet.
If there are any experts who know the RK3399’s MIPI CSI well I could use some help in that regard.


could you share the devterm file for freecad ?

I am working with the meshes supplied by Clockwork Pi directly, but did some decimation to make it easier to render.
I tried converting them to solids but the meshes are too detailed for that.

Here’s a FreeCAD file with the meshes separated:

Also check out the git here:

1 Like

Wow I am slow to this awesome set of developments!! But is there any room for last minute suggested carts?

Pcie breakout to stick something like the rpi2040?

Some way to stick an ssd and possibly boot from it?

And this one I can’t get out of my head: a cassette tape record and playback? For making backups if course :wink:

Pcie breakout to stick something like the rpi2040?

I tried searching for an PCIe bridge chip, no dice so far.
You can however put a RPI pico via USB without any problems.

Some way to stick an ssd and possibly boot from it?

Searched for a chip that bridges USB to mSATA, and there is one actually, the Renesas D720231A.
Tough the availability of this one is not great, LCSC has it on pre-order only.
I mean theoretically possible, but I’d rather work on the software right now before spreading even thinner with more cartridge designs.

And this one I can’t get out of my head: a cassette tape record and playback? For making backups if course :wink:

Sadly there’s not enough room to fit a mechanism, a cartridge is pretty much the size of a cassette already. Having the mechanism outside of course can work, but that would be rather top heavy and look a bit silly. Then there’s the issue that cassette mechanisms nowadays suck, so it’s not worth it in my opinion.

I did investigate the possibility of installing 2.5" SATA drive in the expansion bay.

  1. Form factor;
    Thinner drives like SSD will fit, but thicker (still within valid 2.5" form factor…) ones like the spinning rust won’t.
  2. Power
    Again. SSD can be properly powered by a USB-sata cable, while spinning disks cannot, resulting in the drive restarting constantly.

You also have these usb-c