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StrangeCart


speccery

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Off-topic, but hey it's my thread and I will probably also create a cartridge case for the StrangeCart.
Here are a couple 3D printed "base boards" I've been lately working on. The pictures are not great, I didn't care to setup my proper light. As you can see in these examples there are mounting screw posts for the circuit boards, some wiring holes and places for Cherry MX mechanical switches. These designs keep evolving, but at least so far they're in my opinion pretty great for noodling around. 

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This bigger design below has two "base boards" and some supporting rods connecting the two below the display. The display is an Adafruit 3.5" 480x320px display. Then there is the CPU board, MIDI interface board and the audio DAC board. I'm still working on the software, but the display works (actually both of them work simultaneously), and the DAC board outputs a stereo saw wave at 48kHz sample rate. It uses double buffered DMA for audio output and interrupt based audio generation. The buttons don't yet do anything, I am actually just now printing another button mount to support more buttons. I'm going to use this setup to build a software synthesiser, which is something I've thinking about a long time.

IMG_9045Large.thumb.jpeg.e14f14a0bc452b28faeda35e153dda78.jpeg

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I been reading thru this thread @speccery and I was wondering if you have any strangecart boards available, and if possible would you be willing to ship one to Canada and for what cost, I love to see how it works in person, and possibly use it for some of my own cartridge software projects I been working on. Thanks.

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12 hours ago, Gary from OPA said:

I been reading thru this thread @speccery and I was wondering if you have any strangecart boards available, and if possible would you be willing to ship one to Canada and for what cost, I love to see how it works in person, and possibly use it for some of my own cartridge software projects I been working on. Thanks.

Thanks for the interest - and looking at the thread, it is a very long one by now...
I'd be happy to deliver you a board, I should have a few immediately available and if not I can put together a couple over the weekend. The price is 50 EUR + shipping. Please note that all boards are hand assembled by me so should be treated as prototypes. Having said that, I take all boards I've sent through an extensive test list and my understanding is that they all have worked fine.

You have probably seen the wiki at GitHub , it should give you a pretty good idea what to expect.

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3 minutes ago, speccery said:

Thanks for the interest - and looking at the thread, it is a very long one by now...
I'd be happy to deliver you a board, I should have a few immediately available and if not I can put together a couple over the weekend. The price is 50 EUR + shipping. Please note that all boards are hand assembled by me so should be treated as prototypes. Having said that, I take all boards I've sent through an extensive test list and my understanding is that they all have worked fine.

You have probably seen the wiki at GitHub , it should give you a pretty good idea what to expect.

Thanks I will send you a private message with my address and info tomorrow so we can figure out shipping costs and go from there.

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7 hours ago, speccery said:

Thanks for the interest - and looking at the thread, it is a very long one by now...
I'd be happy to deliver you a board, I should have a few immediately available and if not I can put together a couple over the weekend. The price is 50 EUR + shipping. Please note that all boards are hand assembled by me so should be treated as prototypes. Having said that, I take all boards I've sent through an extensive test list and my understanding is that they all have worked fine.

You have probably seen the wiki at GitHub , it should give you a pretty good idea what to expect.

Hi, if you are building additional ones. Would you consider selling me one as well? I’m located in Germany. 

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  • 2 weeks later...
Posted (edited)

A quick update. I have been testing the boards for shipment. I still need to do a little more testing - the boards have worked fine but I updated my testing procedure a little and found a couple more boards.

 

While I was at this, I also started to work on the StrangeCart firmware some more. I needed to review how I test the boards, which lead to reading the source code, which lead to working on the software...

 

I have added a couple of features, the more interesting of which I will discuss later when I am a bit further, but I think it is pretty interesting - well for me at least.

 

The smaller and less interesting new feature is a helper: during testing I couldn't immediately locate my serial to USB FTDI dongles. On searching I did find a few (I am sure I have more), but they were all connected to various projects and I didn't want to detach them. I was thinking I should not have this problem, since I literally have dozens of microcontroller boards, many of which I have designed and support both USB and serial interfaces. I got hit by the not invented here syndrome, so I added USB to serial conversion capability into the StrangeCart firmware.  For background information, I use the virtual serial port over USB connection to the StrangeCart all the time. For example, when I am testing the boards, I download BASIC programs to the flash memory of the StrangeCart using XMODEM over the USB serial port:

dl_fs DIM.BAS  

xmodem receive to SPIFFS
CCCCCCCCC
xmodem return code: 128

The dl_fs command expects a filename and then XMODEM transmission, and the StrangeCart writes the received data to the flash chip. That enables me to see that things work properly with the flash chip. [In this case it was a very small BASIC program which can then either be loaded from TI Basic using "OLD SCD1.DIM.BAS" or directly loaded to the StrangeCart's own BASIC interpreter with "old DIM.BAS" on the StrangeCart serial console. Save SCD1.DIM.BAS also works for saving if there is another method of getting the BASIC program into the TI.]

 

I now added a new command usb2serial:

usb2serial

Entering USB to serial converter mode. Exit pressing S2 or S3.

 

After this, the StrangeCart will pipe data from the virtual USB port to a physical UART (there is a pin header on board, the serial port is a 3.3V port but I think it's 5V tolerant) and vice versa. Currently the settings are fixed to 115200, 8N1. The buttons S2 and S3 are buttons used to change cartridge images normally, but in this case pushing one of them will terminate the USB to serial conversion mode.

 

This is a small feature, but now I only need two StrangeCarts to test the UART pins on the boards :) 

Edited by speccery
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  • 2 weeks later...
  • 2 weeks later...

A short update: I have been glad to see that multiple people have had interest in the StrangeCart project, and I've been on the past several evenings building boards. Also testing a new method for these boards - I bought a bigger hot plate for board assembly. However I couldn't find the stencil for the boards, so I applied solder paste manually, and quite expectedly there was way too much paste and quite a lot cleaning work to be done as a result. I also have been testing a new flux - which works great but is super easy to over apply. I also learned that it was not a good idea to put the USB connectors and 32768Hz clock crystals in at this phase. I had to remove them from all the boards, clean all the flux and reflow them with a hot air. My TI-99/4A has also been a bit temperamental, so I will need to continue testing with that. On the positive side my test and assembly processes have been improved. At some point I will make a revision of the board to make them a little easier to build. For instance right now there are a few components on the underside, mainly bypass capacitors. I want to bring all the components to the top and I will also order a new stencil at that point, that will greatly increase the assembly speed in the future.

 

I was planning to send out boards this week, but that is not going to happen as I have business trip starting on Saturday and not enough time get these tested before that. But hopefully next week I will be able to ship some boards. 

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StrangeCart barbecue on-going.

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1 hour ago, speccery said:

image.thumb.jpeg.be6415d195d9bca64f75c85cfcfdafb8.jpeg

StrangeCart barbecue on-going.

PCboard BBQ looking good. I am sure you figure out everything. Enjoy your business trip and looking forward to seeing one in person soon once you have ironed out the issues and shipped them out later on this month.

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Thanks @Gary from OPA. Yes I am not concerned about getting them working; two of the boards I tested already earlier completely and they are were working. My test TI-99/4A is just not a happy camper right now. Even so some of the carts do work on it already. I need to take it apart and clean the connectors. I have done that in the past and I have several other consoles as well.

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A short update. I’ve been consumed by work, now a stretch of 10 days without pauses, worked through the weekend, and long days.
 

Anyway today after work i took a bit of time to checkout where I was with the strangecarts I was working on before, and I now have 3 which pass all tests. Ready to ship. I think the remaining I built will likely also work after potential minor tweaks. It’s a bit odd what kind of issues I had, my automatic test routines scan for shorts and check each pin - that meant that the dominant problem was lack of connection, on one board address line A5 was not connected even if with good magnification I was sure it was ok. On another board D6 and D7 were “in the air”, a bit of solder fixed those.

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