The RS-232 protocol
Added 2022-10-31 18:26:22 +0000 UTCNew video? Yes! It's been a while... But I'm getting back to the 6502 computer with plans to add a serial interface, which will allow for a ROM monitor and ultimately a more functional computer. Anyhow, this video gets started by looking at the electrical and timing characteristics of the RS232 protocol.
As always, I appreciate your support! I realize it's been a while, so if you weren't expecting a post or otherwise aren't interested, my policy is always that if you simply ask, I'll refund your contribution. And of course, please let me know if you catch any errors or confusing bits.
Thanks again!
-Ben
Comments
Good to have you back indeed !
Fabien Wernli
2022-11-28 10:17:53 +0000 UTCCongratulations on your 1 millionth subscriber !
Michael McDonnell
2022-11-09 00:03:05 +0000 UTCLol, I literally cancelled on Friday. If you’re back I’m back.
Jim McCaslin
2022-11-07 05:34:55 +0000 UTCI 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).
Peter Larsen
2022-11-06 21:01:03 +0000 UTCAt 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
2022-11-06 11:03:28 +0000 UTCI'm currently ill in bed and it's great to have you back making videos.
Corin Baurmann
2022-11-06 10:35:55 +0000 UTCGreat to have you back!!!!!
Daniel Varga
2022-11-06 06:27:28 +0000 UTCGlad to have you back, Ben!
Chris Bates-Keegan
2022-11-05 15:44:11 +0000 UTCJust happy you're alive and well :)
Jason Bowen
2022-11-05 15:31:37 +0000 UTCWelcome back! I am excited to check out this new video.
Ryan Helinski
2022-11-05 15:22:57 +0000 UTCWelcome back, Ben!
Tim Oriol
2022-11-05 06:11:14 +0000 UTCReturn of the king
Cameron Peck
2022-11-03 21:33:35 +0000 UTCReally 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.
Martin Noble
2022-11-03 20:56:01 +0000 UTCgood to have you back
Andy Chang
2022-11-03 11:43:29 +0000 UTCat 22:56 you said 1ghz i think you meant 1 mhz
Michael McDonnell
2022-11-02 22:15:43 +0000 UTCI sort of knew what 8n1 (or 8e1, etc) meant but not at the bit level. It is great to see a video from you.
Michael McDonnell
2022-11-02 22:11:14 +0000 UTCYAY!! We missed you and are thrilled to have you back!!
-
2022-11-02 17:08:06 +0000 UTCI thoroughly enjoyed that, thanks! Well worth the wait.
Dave MInter
2022-11-02 12:44:27 +0000 UTCI'm just glad you're okay, and back making excellent videos! I learn so much from you!
Adrian Cochrane
2022-11-02 07:17:28 +0000 UTCSo glad you're back!
Jonathan Turner
2022-11-02 00:14:47 +0000 UTCWelcome Back; glad to see you are ok. Also great video :D
Danzar
2022-11-02 00:12:56 +0000 UTCYou are back! Great!
Lukasz Pacholik
2022-11-01 22:30:38 +0000 UTCI'm so glad you're back!!
Kerry Allan
2022-11-01 22:14:39 +0000 UTCAlways happy to see a Ben Eater video! Hope to see you expand the 8-Bit BB Computer someday.
David Courtney
2022-11-01 21:50:33 +0000 UTCWelcome back! Looking forward to watching this!
Auctoris
2022-11-01 21:10:15 +0000 UTCGreat 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.
Ivan Toshkov
2022-11-01 20:41:44 +0000 UTCRestored my faith in humanity... all is not lost; thank you for the triumphant return and for affirming that serial is not dead!
Michael Weitman
2022-11-01 19:53:16 +0000 UTCWelcome back!!
Jo Ga
2022-11-01 19:36:25 +0000 UTCOdd transition at 9:27
David Dawkins
2022-11-01 19:13:00 +0000 UTCWonderful to see you back
David Dawkins
2022-11-01 19:01:19 +0000 UTCHappy to see you back, hope you're doing ok!
alisianoi
2022-11-01 16:14:51 +0000 UTCWelcome back, Ben. I hope you and yours are O.K.
Fred Leckie
2022-11-01 16:04:51 +0000 UTCTiny mistake, at 23:00 you say "1 Gigahertz clock" by mistake instead of "Megahertz". Thank for the video!
Matt Shaile
2022-11-01 13:32:37 +0000 UTCI 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
Nik Klassen
2022-11-01 12:27:59 +0000 UTCAt 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.
Elekes Karoly
2022-11-01 12:09:16 +0000 UTCWhat an amazing video to come back with!
Dylan Speiser
2022-11-01 06:25:38 +0000 UTCGlad 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.
Jeff
2022-11-01 05:59:50 +0000 UTCYay 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!
LemonRamen Games
2022-11-01 05:01:55 +0000 UTCSadly no :(
Jeff Geerling
2022-11-01 01:39:54 +0000 UTCSo good to hear from you, Ben! Welcome back. You've definitely been missed.
Mike Swanson
2022-10-31 23:59:59 +0000 UTCWow! I for sure though you had left us all. Very happy (and relieved) to hear from you again.
Magnus Hugemark
2022-10-31 23:16:28 +0000 UTCGreat 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 :)
Nick
2022-10-31 22:59:41 +0000 UTCWelcome babies, Ben.
Robert Brown
2022-10-31 22:45:52 +0000 UTCGlad to see you back and hope all is well or at least better.
Steve Robillard
2022-10-31 22:42:48 +0000 UTCGreat 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.
Kris Kennaway
2022-10-31 22:41:57 +0000 UTCDoes Red Shirt Jeff have a breadboard 6502?
Douglas Moore
2022-10-31 21:51:38 +0000 UTCAt about 23:03, you said, "... with a 1GHz clock". Pretty sure you meant to say "one megahertz".
Mark Day
2022-10-31 21:51:29 +0000 UTCFYI, 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.
Mark Day
2022-10-31 21:44:47 +0000 UTCHello 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.
Edward Meewis
2022-10-31 21:39:20 +0000 UTCGreat to see you making videos again!
Jim Knowler
2022-10-31 21:32:04 +0000 UTCWelcome back! :)
Spencer Ruport
2022-10-31 21:14:07 +0000 UTCReally enjoyed it. Looking forward to the next videos and the associated kit.
Scoth Harris
2022-10-31 21:01:32 +0000 UTCYes, 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!
Shelton
2022-10-31 20:49:50 +0000 UTCHe already demonstrated that in three earlier videos. You may want to review those. - Ed.
Edward Meewis
2022-10-31 20:24:04 +0000 UTCWoo-hoo! Can't wait to get a chance to sit down and watch this one!
Jeff Jetton
2022-10-31 20:11:10 +0000 UTCSo good. Enjoyed every second of the video. Glad you‘re back!
Joffito
2022-10-31 20:10:18 +0000 UTCHoly crap welcome back Ben!
Jeremy Tice
2022-10-31 20:05:07 +0000 UTCWelcome 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.)
Shelton
2022-10-31 20:00:25 +0000 UTCGreat video, glad to see you're back!
John Castle
2022-10-31 19:34:04 +0000 UTCI wanted so much to add serial to my build! This will surely be super helpful! Welcome back, Ben!
Vito Sartori
2022-10-31 19:23:52 +0000 UTCExciting to see it! I love your deep dives into these protocols that I use often (abstracted through libraries) but never really dove into much.
Jeff Geerling
2022-10-31 19:20:33 +0000 UTCBeyond elated to see this. It may be unfair of some of us to be concerned but you are a part of our existence now.
David Craig
2022-10-31 19:19:10 +0000 UTCSuper glad to see you back!
James Helms
2022-10-31 19:06:37 +0000 UTCThanks for the video
Thomas Eriksen
2022-10-31 19:05:25 +0000 UTCAnd 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.
Hugo Dahl
2022-10-31 18:59:26 +0000 UTCWelcome back Ben! We missed you! :)
Naphtali Levy
2022-10-31 18:52:29 +0000 UTCYay, making a big batch of popcorn to enjoy this video!
Xavier
2022-10-31 18:49:38 +0000 UTCWelcome back :)
AlesK56
2022-10-31 18:45:52 +0000 UTCSo good to see you back!
Richard
2022-10-31 18:44:07 +0000 UTCWe were all worried about you. Hope all is well and that you are in good health.
Kevin Snaden
2022-10-31 18:41:21 +0000 UTCDude I've been legitimately worried about you! Glad to see you're seemingly good and back at it! Excited to watch the video!
Tim Soderstrom
2022-10-31 18:39:11 +0000 UTCSo glad you’re back!
Tyler Arbogast
2022-10-31 18:38:02 +0000 UTCYESSSS, so happy for more of your work
Danny M
2022-10-31 18:35:48 +0000 UTCSo glad to hear of your return!
Joe Rork
2022-10-31 18:34:58 +0000 UTCI couldn’t agree more
Ori Shamir
2022-10-31 18:34:28 +0000 UTCChristmas has come early!
Douglas Moore
2022-10-31 18:28:35 +0000 UTC
