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Oh no, GPIO. That means the computer will be able to connect to the world. Now the robot uprising is upon us and we're all doomed!

One of my favourite episodes, looking forward for the next few: how the CPU makes friends

I'd never really thought about how GPIO might be implemented in hardware on microcontrollers. Very interesting to see how simple & elegant it is!

Like your method of showing the schematic alongside the breadboard. As well as that you show actual gate function rather than just black boxes like some UKposts channels...

Every computer needs some GPIO pins, and you deserve something a bit simpler to recover a bit between the VGA stuff :)

Interesting as always. And I'm kind of impressed by how well you've tamed your assembler code base. You were able to expose the GPIO pins and add new functions so quickly I was honestly amazed. LOL

I love how much circuitry is there just to show some different LEDs when you press a single button. It reminds me of people implementing CPUs in Minecraft - emulating simple devices using much more complicated ones. There's just something satisfying to all that complicated stuff being used to implement the basics that it started out with. Something akin to bootstrapping your own programming language in the same language.

Thanks James. I thought basic GPIO would be faily easy to implement. I enjoyed this one a lot because I could understand everything you did. Take care.

We are truly blessed. On the same day as James uploads a video on connecting to the outside world, Ben Eater is uploading a video on connecting his 6502 breadboard computer to the (serial) world.

Fascinating project!! And it looks awesome 👌

That was smooooth! It really shows how mature the system is. I can't wait for the next videos. Thank you very much for the awesome content.

I remember on the BBC Micro, we had the User Port 'cus I don't think anyone said GPIO back then... But some of our teachers loved it, because it was the route to connecting all manner of exotic cr... erm stuff up to the computer.... ... yeah, you gotta have some GPIO.

Always nice to take a break on a complex project and work on something simple.

As always, thanks for sharing. Just out of curiosity: Instead of using a combination of a 74LS574 and a 74LS04, you could have used a single 74LS373 as well. That chip is especially designed for that kind of application. What was your reason not to go that route?

Making a EPP/ECP parallel port would take a lot of parts. ;)

Hi James, I very much enjoy this whole series and pick some of your designs and techniques for my own build. Regarding this GPIO circuit this would „only“ be a in- AND an output port because each pin is either in or out but not generally usable in both directions (hence the name GPIO) for this there must be an 3rd register to set the direction, and the pins of the in port an the out port have to be multiplexed by this register and an analog switch - or so I always thought. Anyway I think the point here being simplicity that’s the way to go and as a bonus there are 16 lines 8 in and out each. Wish you and everyone happy Easter!

Ive been watching for your new video.

Awesome brainpower at work

Brilliant. I'll be most likely using 573 in my design (due to timings), this looks like The Way To Do It. Thanks.

It's crazy how far you've come with this computer. I like the idea of adding more connectivity like the GPIO and UART. Do you think it would be possible to go further and add some sort of primitive networking like 10base-t with LLDP? It seems like it would be possible combining the designs you used for the VGA and UART.

This might be a simple video, but opens up to all kinds of interesting possibilities. One possibility that comes to mind is access to an SD Card which suddenly gives you access to a couple of GB of storage.

super chill

This is a nice start, would be cool to add a little state engine and a buffer to this so you can emulate some serial interfaces without having to bit bang using the processor.

I am so happy that you made your thumbnail cleaner😅

wow, interesting, thanks

Suggestion: Add a mass storage (Compact Flash, most likely) interface; Make a simple filesystem driver (Any basic, optionally hierarchical file system should work); Write a text editor that can read and write files on that drive, as well as an assembler and runtime program that act on files on the drive This should make the computer entirely self-serving, provided you have a serial terminal [or an emulated version of one], since you can write files on the computer, compile them in-situ, and run them right then and there. Maybe even lays the groundwork for a full rework of the firmware, where the ROM doesn't have the assembler/disassembler/etc. anymore but gets a 'boot from HDD' option that loads and runs the boot sector.

The LC display can also be controlled with GPIO. Or you implement an I2C bus. This then gives you access to many sensors.

At around 7:00 you have the pinout for the 74xx541 shown which you aren't using. Great video though! It's a great day, a James Sharman video and a Ben Eater video release around the same time!

congrats for "success at the first try". Do you want to protect those GPIOs somehow from strange handling / abuse, or is this something you put away for jam because you consider it kind of a controlled environment?

Will there be more CPU updates? Or is it in its final state? Maybe some new cool functionality like GPR banks or an arithmetic coprocessor for hardware multiplication and division? Or will it only be peripherals from now on? Also, would like to get a separate video on instruction set, what instructions there are and how are they encoded and why where they chosen, because it's been so long and all in separate videos I've already kinda forgot what instruction set limitations there are... Also would be interested to know about some cut features, something you've wanted to add to your build but decided not to...

thats DOPE , i have a question . the name of the cpu/computer is jam-1 , how much more are you planing to do with it before you move on to jam-2 or something like that ? what would you like to chande with jam-2 ?

The MCUs I've used so far seem to have more than one port. Do you have any future plans for Dev 13? The possibility of not needing an adapter board to run a 16-bit device could be useful. How hard is it to develop plug-and-play code? That could be a great topic for either this series or the next. If so, would it make any sense to add standard connectors like PS/2 or D-sub to the final GPIO board as connectivity options?

very interesting , especially the part about a switch program being the baintent underutilization of resources you have or was it overutilization .. me english not so good in technical. anyway as you stated blink program on arduino is making something overcomplicated to perform simple tasks i bet your cpu is not up to the task i am trying to shoehorn atmega8 ic in place of arduino :] and that being a dcc decoder for a train layout ...well if you could run at 16 mhz your cpu probably would be up to task of controlling model trains or being a train too but that is just the clock frequency for commonly used atmel and pic microcontrollers by the way happy easter

You are changing the load signal after the output enable! which could cause problems if you were running at the limits of the chips but in this case your get away with it I expect. As the /OE only one propagation delay before the latch signal.

What is the piece called that you are using to short all the led array's output pins together? Currently I am only able to short the pins if I have an individual wire for each output pin. Tried looking but haven't been able to find it.

Fun :-)

I wonder if your gona go down the same route RPI did where their UART runs on the GPIO header?

I hope you add a thermal printer. It would be extremely trivial, but would be neat nonetheless.

What's the software you're using to make your schematic? I've googled quite a bit but I can't find any program that looks like the one you're using.

a lot of soldering, reminds me of raspi or doing several pico, which was still less than here ...

a newbie here. maybe you can replace the two 555s with a single 556? excellent videos! keep it up!

"This isn't DOS dufus!" LOL!😆

I can see the utility and the need for GPIO, but honestly not a very exciting video series to me. That doesn't mean I won't watch, comment or enjoy them, just that it isn't very exciting to me.