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The RS-232 protocol

🕑 Added 2022-10-31 18:26:22 +0000 UTC

Comments

Fabien Wernli

Good to have you back indeed !

Michael McDonnell

Congratulations on your 1 millionth subscriber !

Jim McCaslin

Lol, I literally cancelled on Friday. If you’re back I’m back.

Peter Larsen

I admire your way of explaining technical topics in ways that doesn't make it sound like you're speaking down to the viewer. A lot of your videos you take the viewer on a discovery journey and it feels clear you're purposedly getting into the hurdles you to illustrate points, making the viewer appreciate a better understanding of what goes on. I tried to explain RS232 to a friend and didn't even come close to this. Great video (as always).

Corin Baurmann

At 24:20, by setting the counter in half_bit_delay to #6 instead of #13, we are not really waiting exactly half a bit though, are we? because the original counter of 13 included the time it took the routine to read the bit, whereas with half_bit_delay, we are waiting before the routine gets executed. Still works, because reading at 1/3 of a bit is fine with a well tuned clock.

Corin Baurmann

I'm currently ill in bed and it's great to have you back making videos.

Daniel Varga

Great to have you back!!!!!

Chris Bates-Keegan

Glad to have you back, Ben!

Jason Bowen

Just happy you're alive and well :)

Ryan Helinski

Welcome back! I am excited to check out this new video.

Tim Oriol

Welcome back, Ben!

Cameron Peck

Return of the king

Martin Noble

Really great to have a new video. Seeing the bits on the scope really helps with understanding how the protocol works and how it copes with lack of clock transmission.

Andy Chang

good to have you back

Michael McDonnell

at 22:56 you said 1ghz i think you meant 1 mhz

Michael McDonnell

I sort of knew what 8n1 (or 8e1, etc) meant but not at the bit level. It is great to see a video from you.

-

YAY!! We missed you and are thrilled to have you back!!

Dave MInter

I thoroughly enjoyed that, thanks! Well worth the wait.

Adrian Cochrane

I'm just glad you're okay, and back making excellent videos! I learn so much from you!

Jonathan Turner

So glad you're back!

Danzar

Welcome Back; glad to see you are ok. Also great video :D

Lukasz Pacholik

You are back! Great!

Kerry Allan

I'm so glad you're back!!

David Courtney

Always happy to see a Ben Eater video! Hope to see you expand the 8-Bit BB Computer someday.

Auctoris

Welcome back! Looking forward to watching this!

Ivan Toshkov

Great video! Thank you. I think you should name it "The RS-232 protocol" though. Even if it's slightly inaccurate, it will generate more views IMO.

Michael Weitman

Restored my faith in humanity... all is not lost; thank you for the triumphant return and for affirming that serial is not dead!

Jo Ga

Welcome back!!

David Dawkins

Odd transition at 9:27

David Dawkins

Wonderful to see you back

alisianoi

Happy to see you back, hope you're doing ok!

Fred Leckie

Welcome back, Ben. I hope you and yours are O.K.

Matt Shaile

Tiny mistake, at 23:00 you say "1 Gigahertz clock" by mistake instead of "Megahertz". Thank for the video!

Nik Klassen

I got so much out of the breadboard computer series and I've been patiently waiting for a new video just so I could support you

Elekes Karoly

At first, I thought, that you will use the R65C51 chip, and said to myself, oh I already implemented that on my computer, my jaws dropped when I saw that you are using a single transistor.

Dylan Speiser

What an amazing video to come back with!

Jeff

Glad to hear from you! Its fun to see you do deep dives into protocols that I use at work. We still use rs-232 in a handfull of locations to interface test equipment on an assembly line.

LemonRamen Games

Yay so glad to see a new post! I found your account a few months ago and I managed to build the 8 bit computer and 6502 computer, working on the graphics card next. But I was very sad to see that you had stopped uploading months before I encountered your channel. Super glad that your back, keep up the great work Ben!

Jeff Geerling

Sadly no :(

Mike Swanson

So good to hear from you, Ben! Welcome back. You've definitely been missed.

Magnus Hugemark

Wow! I for sure though you had left us all. Very happy (and relieved) to hear from you again.

Nick

Great to see you back. I recently discovered your excellent videos, and was somewhat dismayed to see you weren't active online. I'm feeling very inspired by your 8-bit computer and 6502 series, and I remarked to a friend (who has built your 8 bit computer) that it was a shame you didn't seem to be active, and he mentioned this new post, so here I am, a brand new backer :)

Robert Brown

Welcome babies, Ben.

Steve Robillard

Glad to see you back and hope all is well or at least better.

Kris Kennaway

Great to see another video! Some small corrections on the cycle counting: JSR is 6 cycles JMP is 3 conditional branches are 2 if not taken and 3 if taken (plus another one if crossing a page boundary) This probably doesn't change things enough to matter (since it obviously works), because it's still within tolerances when reading 8 bits after the start bit synchronization.

Douglas Moore

Does Red Shirt Jeff have a breadboard 6502?

Mark Day

At about 23:03, you said, "... with a 1GHz clock". Pretty sure you meant to say "one megahertz".

Mark Day

FYI, there is an alternate way to get the input bit into the carry flag, if you can wire the input to either bit 7 or bit 0 of PORTA. You do a LDA PORTA followed by a ROL (for bit 7) or ROR (for bit 0). Of course, this modifies the accumulator, so you have some choices: * Push and pull the A register around the LDA PORTA / ROL(R) * Keep the input byte in RAM (you would do ROR $addr to shift in the bit) * If you're not using PORTA for output, you could ROL/ROR PORTA directly to move the input bit into the carry flag, without changing the accumulator. Note that all of these avoid conditional branches, which makes things easier if you're counting cycles for timing purposes.

Edward Meewis

Hello Ben, Thank you for another great video! Other avenues to explore: Flow control (RTS/CTS, handshakes), differential signals (LVDS) or analog electronics (how to generate a negative voltage from a positive one, charge pumps). Maybe you already had those planned. Best regards, Ed.

Jim Knowler

Great to see you making videos again!

Spencer Ruport

Welcome back! :)

Scoth Harris

Really enjoyed it. Looking forward to the next videos and the associated kit.

Shelton

Yes, I remember those videos. Thanks for reminding me. In my memory, they weren’t related to the 6502 “series”, though. Might be an opportunity to reference those older videos in the current one!

Edward Meewis

He already demonstrated that in three earlier videos. You may want to review those. - Ed.

Jeff Jetton

Woo-hoo! Can't wait to get a chance to sit down and watch this one!

Joffito

So good. Enjoyed every second of the video. Glad you‘re back!

Jeremy Tice

Holy crap welcome back Ben!

Shelton

Welcome back. This is great. I like that you're moving to the ability to use a terminal emulator to communicate with it. But how about "just" a keyboard (like an old serial or PS2 style). Some of us may actually have an old one. I'm not suggesting to edit the video -- other than perhaps to mention if it would be at all possible or not (even if not wise) to connect just a keyboard. (And, maybe this is for a later video where you introduce the Serial chips.)

John Castle

Great video, glad to see you're back!

Vito Sartori

I wanted so much to add serial to my build! This will surely be super helpful! Welcome back, Ben!

Jeff Geerling

Exciting to see it! I love your deep dives into these protocols that I use often (abstracted through libraries) but never really dove into much.

David Craig

Beyond elated to see this. It may be unfair of some of us to be concerned but you are a part of our existence now.

James Helms

Super glad to see you back!

Thomas Eriksen

Thanks for the video

Hugo Dahl

And now, all these names and values that I "just knew" make so much more sense! Great intro to serial communications. Minor note: right around 23:02-23:03 you said "...each clock cycle is a micro-second with a one gigahertz clock", when you likely meant "one megahertz clock". Should be fairly obvious you meant "megahertz" since you went over the speed, timing and clock earlier in the video.