Answers.Body: <p>Uli posted a link in a comment to <a href="https://lgauge.com/technic/LEGOInterfaceA/9750(1093).htm" rel="nofollow noreferrer">https://lgauge.com/technic/LEGOInterfaceA/9750(1093).htm</a> which has a link to <a href="http://isodomos.com/Lego-Sets/1093.html" rel="nofollow noreferrer">http://isodomos.com/Lego-Sets/1093.html</a> , that link is dead but archive.org has a copy <a href="http://web.archive.org/web/20081121054400/http://isodomos.com/Lego-Sets/1093.html" rel="nofollow noreferrer">http://web.archive.org/web/20081121054400/http://isodomos.com/Lego-Sets/1093.html</a> both sites have the pinout, but the latter site also confirms the logic levels as 5V TTL.</p>
  <p>I will repeat the pinout here, in case those sites disappear.</p>
  <ul>
  <li><p>Pins 1 and 3: 5V</p>
  </li>
  <li><p>Other odd numbered pins: Ground</p>
  </li>
  <li><p>Even numbered pins 6-16: Outputs 0-5</p>
  </li>
  <li><p>Pins 18 and 20: Inputs 6 and 7</p>
  </li>
  </ul>
  <p>Unlike the interface B which is a somewhat-intelligent device that communicates over RS-232 the interface A seems to just use straight digital IO lines. For bi-directional control of motors the outputs can be used in pairs.</p>
  <p>The pinout seems to be an exact match for the user port on a BBC micro. I suspect this is not a coincidence.</p>
  <p>It would not be difficult to hook this up to something more modern, a 5V Arduino could probably hook up directly. For a Raspberry Pi you would want something to shift the levels, I'd probably use HCT logic running off 5V for the signals from the Pi to the interface A (this may not be strictly needed) and LVC logic running off 3.3V for the signals from the interface A to the Pi.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-08-13T09:12:44.207Z
Answers.Text: "[Some findings with Interface A](https://ofalcao.pt/blog/series/lego-interface-a)". Blog post from 2017 (ofalcao.pt)
Answers.UserDisplayName: Uli
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-08-13T13:44:56.507Z
Answers.Text: Yeah, lots of different ways to skin this cat.
Answers.UserDisplayName: Peter Green
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2020-08-13T01:03:21.560Z
Answers.LastActivityDate: 2021-02-26T05:09:42.297Z
Answers.LastEditDate: 2021-02-26T05:09:42.297Z
Answers.UserDisplayName: Peter Green
Answers.Body: <p>@Mark I can help you. My website <a href="http://www.brickhacks.com" rel="nofollow noreferrer">www.brickhacks.com</a> is all about Interface A. It has schematics for all of the hardware, etc.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-10-29T22:06:35.777Z
Answers.Text: While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - [From Review](/review/late-answers/12035)
Answers.UserDisplayName: Alex
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-10-29T19:17:29.680Z
Answers.LastActivityDate: 2023-10-29T19:17:29.680Z
Answers.UserDisplayName: Evan Koblentz
Body: <p>I have a Technic Interface A with the cables but lack the printed circuit board (PCB) for PC that I need to use it for automating my models. The card when it was for sale had markings of Lego 9771 and I assume this to be the part number.</p>
  <p>Ideally I would like an original card but is there a way of getting a 3rd party card? Or another idea might be if someone does manage to make such an interface please consider building it to run multiple Interface A and/or B modules simultaneously.</p>
  <p>I think that I may have parts that run on almost if not all of the powered interfaces that Lego has been kind enough to release. I would be quite grateful indeed if I were able to use them together in my sizeable Lego projects.</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-08-12T08:12:54.217Z
Comments.Text: Hi Mark and welcome to Bricks.SE! I for one have a hard time picturing your situation as I haven't heard of "Technic Interface A", so could you please upload a photo of your part? The 9771 number does not match any known sets and none of the [matching parts](https://brickset.com/parts?query=9771) are related to Technic.
Comments.UserDisplayName: zovits
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-08-12T08:30:20.357Z
Comments.Text: Does this help? Technic Interface A on [lgauge.com](https://lgauge.com/technic/LEGOInterfaceA/9750(1093).htm)
Comments.UserDisplayName: Uli
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2020-08-13T09:26:08.827Z
Comments.Text: @Uli Thanks, I have learned something new today :)
Comments.UserDisplayName: zovits
Tags: <technic><powered-up><vintage><education>
Title: Interface A missing PCB
UserDisplayName: Mark
ThreadText: # Interface A missing PCB
  
  (Asked by: username_0 on 2020-08-12)
  
  I have a Technic Interface A with the cables but lack the printed circuit board (PCB) for PC that I need to use it for automating my models. The card when it was for sale had markings of Lego 9771 and I assume this to be the part number.
  
  Ideally I would like an original card but is there a way of getting a 3rd party card? Or another idea might be if someone does manage to make such an interface please consider building it to run multiple Interface A and/or B modules simultaneously.
  
  I think that I may have parts that run on almost if not all of the powered interfaces that Lego has been kind enough to release. I would be quite grateful indeed if I were able to use them together in my sizeable Lego projects.
  
  **Tags:** technic, powered-up, vintage, education
  
  > **Comments:**
  > **username_1**: Hi Mark and welcome to Bricks.SE! I for one have a hard time picturing your situation as I haven't heard of "Technic Interface A", so could you please upload a photo of your part? The 9771 number does not match any known sets and none of the [matching parts](https://brickset.com/parts?query=9771) are related to Technic.  
  > **username_2**: Does this help? Technic Interface A on [lgauge.com](https://lgauge.com/technic/LEGOInterfaceA/9750(1093).htm)  
  > **username_1**: @username_2 Thanks, I have learned something new today :)  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_3 on 2020-08-13. Score: 3
  
  Uli posted a link in a comment to <https://lgauge.com/technic/LEGOInterfaceA/9750(1093).htm> which has a link to <http://isodomos.com/Lego-Sets/1093.html> , that link is dead but archive.org has a copy <http://web.archive.org/web/20081121054400/http://isodomos.com/Lego-Sets/1093.html> both sites have the pinout, but the latter site also confirms the logic levels as 5V TTL.
  
  I will repeat the pinout here, in case those sites disappear.
  
  * Pins 1 and 3: 5V
  * Other odd numbered pins: Ground
  * Even numbered pins 6-16: Outputs 0-5
  * Pins 18 and 20: Inputs 6 and 7
  
  Unlike the interface B which is a somewhat-intelligent device that communicates over RS-232 the interface A seems to just use straight digital IO lines. For bi-directional control of motors the outputs can be used in pairs.
  
  The pinout seems to be an exact match for the user port on a BBC micro. I suspect this is not a coincidence.
  
  It would not be difficult to hook this up to something more modern, a 5V Arduino could probably hook up directly. For a Raspberry Pi you would want something to shift the levels, I'd probably use HCT logic running off 5V for the signals from the Pi to the interface A (this may not be strictly needed) and LVC logic running off 3.3V for the signals from the interface A to the Pi.
  
  > **Comments:**
  > **username_2**: "[Some findings with Interface A](https://ofalcao.pt/blog/series/lego-interface-a)". Blog post from 2017 (ofalcao.pt)  
  > **username_3**: Yeah, lots of different ways to skin this cat.  
  
  ---
  
  ### Answer by username_4 on 2023-10-29. Score: 0
  
  @username_0 I can help you. My website [www.brickhacks.com](http://www.brickhacks.com) is all about Interface A. It has schematics for all of the hardware, etc.
  
  > **Comments:**
  > **username_5**: While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - [From Review](/review/late-answers/12035)  
  
  ---
  
  