Repairing (a possibly common?) Serial Communication Issues on LEGO Dacta Interface-B

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Edited June 27 by Gunners TekZone

[Toastie]

48 minutes ago, Gunners TekZone said:

But for now, I will follow along in these fun technical LEGO discussions!

Yeah, you are right. So we settle on 2A max. for the Interface B 12V AC juicer transformer?

Best,
Thorsten

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Edited June 27 by Gunners TekZone

[Guest]

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Edited June 27 by Gunners TekZone

[dr_spock]

 

6 hours ago, Bliss said:

The original Lego PSU is 12VAC 7VA so we talk basically of 600mA at 12 VAC for the whole box...  It not much...

Can the Box use more amps if we connect a bigger PSU say 12VAC at 2A (24VA)?

No matter USB-C or USB-A, from a computer port it is not like a PD Charger I think...

I would use the USB from a computer to have both DATA and Power.

But anyway, saying this, google tell me:  Most computer USB ports supply 5V of electricity with a maximum current of 0.5A.

So maybe not enough to use the interface at least like the spec...  but still...

How about wiring a USB connector directly to the 5V rail of a PC power supply?  This old PC PSU lists 22A max on the 5V.

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Edited June 27 by Gunners TekZone

[Wapata]

Hello there ! 

I'm not creating a new topic because I think the solution may be here.

I had a particular issue : I can see that i'm sending Data to the Lego Dacta Interface-B as the red light turn off (to think about life etc) but then... no answer. Two interface, a good null modem cable, some jumpers, multiple usb ports, a computer that is cool with serial-usb interfaces... nothing.

But it look like the Interface-B was dead from the factory, despite the control check stickers.

One component is upside down !

So I did solder it back but don't know how to test it, And i have a leg that lead to nowhere.

Can someone check if this leg is "free" ?

I have made pictures whit a light behind, because i never found a good PCB picture on the web.

 

But let's be clear : after all the time spent, if there i;s no "eureka" solution, i would like to use the USB-TTL solution, but there is not a single picture left from @Gunners TekZone  . I know how to follow electronics schematics, not how to create things from nothing

Edited March 16 by Wapata
correcting pictures links

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Edited June 27 by Gunners TekZone

[Wapata]

Of course it does help ! Let's bring the ttl back and test that ! 

Okay... false start, i'm not able to put my hand on a single USB-TTL at home 

Edited March 16 by Wapata

[Wapata]

Let's call that a huge success !!! 

 

Thank you very, very much @Gunners TekZone!

Now I just have to find out why i don't have any TTL converter anymore and see how to make that a little bit more sexy 

Oh i'm so happy right now.. this device never worked since his creation 

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Edited June 27 by Gunners TekZone

[Wapata]

Yes. And i've also seen that i cant put everything back because there is a big red button just in the area i've used... It wasn't obvious one hour ago.

So now i've have to go to aliexpress and chose TTL to USB or TTL to Bluetooth. There is 12 volts, 9Vdc but maybe a 5Vdc can be hidden somewhere 

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Edited June 27 by Gunners TekZone

[Wapata]

If it does work great in 3.3v then it will be 3.3v too. And I've seen somewhere else that the wires can break inside the ribbon cable so I think that your idea is good, plus there is plenty space to put cables here.

Plenty space too to glue the adapter somewhere and make a plate to hold a good old usb-B connector in the sub9 hole.

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Edited June 27 by Gunners TekZone

[Wapata]

I don't think I will ever learn python sadly. But there is also standalone-raspbery work made somewhere here (but out of the interface-B). https://controllab.io/

 

I didn't find any "real" ttl to Bluetooth to use with https://blissca.github.io/lego-blockly/

And my "good old usb-B" is obsolete... There is more usb-C converter now   well... Why not in the end.

[Toastie]

47 minutes ago, Wapata said:

Let's call that a huge success !!!

Oh yes, congratulations!

But what did I miss? There was this wrongly soldered tripod thingy - did you replace that? What actually made the Interface B come back to life? The Arduino soldered directly to the B's microcontroller? I am just curious.

Best wishes,
Thorsten 

[Wapata]

Just now, Toastie said:

Oh yes, congratulations!

But what did I miss? There was this wrongly soldered tripod thingy - did you replace that? What actually made the Interface B come back to life? The Arduino soldered directly to the B's microcontroller? I am just curious.

Best wishes,
Thorsten 

Serial port use 12-15 volts and ttl 3-5 volts for Rx and Tx. But it's kind of the same signal. So with the great help of @Gunners TekZone I was able to find WHERE are those ttl signal. Then I was not able to find back my converters but learned that if you short RST to ground on an Arduino, you can skip the whole Arduino thing and use the Rx and Tx pins as ttl directly connected to the USB port.

So now I know my device is working, still don't know why it never answered back in the beginning but... Whatever now ;-)

[Wapata]

Okay, I've changed my mind after some soldering just before going to work. 

 

 

 

First I will not use the ground anymore as it is the "high voltage ground" and will use the Sub9 ground pin 5 that is isolated from the other one.

Then i will keep the Interface-B as original as possible so i will use the pin 1 and pin 9 of the Sub9 port and create an external device for the TTL to USB convertor. Like that, every single user that want to upgrade his Interface-B can do it whatever if he use the Original Null Modem Cable, a "full" Null Modem Cable, or the TTL convertor.

But then i have not a single clue if you can damage to death the Interface-B if you connect a straight Serial Cable to a computer...

[Wapata]

17 hours ago, Toastie said:

this wrongly soldered tripod thingy - did you replace that

Sorry i've missread your question: i don't know what the black tripod component is but yes i did put it back in place as you can see on the second image. The multimeter said "bip" for each leg and trace... at least for the two traces i'm able to follow. It is a 4 layer PCB but this last leg doesn't seems to be connected to anything.

Then it still doesn't work. Then I take out and back the component, then it still doesn't work. Then I was not able to put my hand on my mini oscilloscope (should be with my TTL interfaces) so I was thinking it's a dead end because every wire and pcb route are good.

After that i've proced to create an account here because every question about old Lego electronic stuff leads here. Then i had to wait for approval, and here I am, asking for help in the very good topic because the pictures are missing. pfiouuu

And somehow also seen that i'm not able to MP one of you for a side question : is it me or there is no documentation on the web about the Lego sensors (like, wiring, pinout, what are they and so on) ? I feel that the temp sensor should be PT100 but have no luck with the search button.

[Toastie]

@Wapata

Wow, that is quite the journey you have taken! And surely tracing a four layer PCB is quite the task, if possible at all with just a multimeter or small oscilloscope. At least the "legs" of the individual components should connect to something - if they are not some type of 3 pin SMD dual diodes, where they only used one diode (here is an example: https://ae.rsdelivers.com/product/nexperia/bav99215/nexperia-100-v-215-ma-diode-switching-3-pin-sot-23/1037576). I vaguely remember (but that could be wrong, need to check) that the IR tower of the RCX used a couple similar devices and one had only two pins attached(?).

With regard to PMs: You need a post count >= 10 (again, not sure about the =, it is maybe > ;) and then you can PM around. So that will be enabled for you any time soon.

LEGO sensors: All the 9V sensors usually used in conjunction with Interface B are fully compatible with RCX/9V Mindstorms sensors. In this regard, Philo's homepage is always a good start (https://www.philohome.com/tech.htm) - here you will also learn about powered vs. unpowered sensors, how to do that, what they do etc. I also had some luck with googling "LEGO RCX sensor circuit diagram" (picture search only) - that will lead to quite some old, but still functioning sites.

Just let me know what you are looking for specifically and I can dig through my files, handwritten pages, and so on. Others here on EB have certainly also valuable information in this regard!!!

All the best,
Thorsten

 

[Wapata]

1 hour ago, Toastie said:

you are looking for specifically

What are those temperature sensors. And by the way the link you gave me is great for the rotary sensor ! For now, all my sensors are wireless, waiting for a new spool of black wires 

Right now the Interface B is not working anymore. New pictures first :

 

So the Pin5 ground doesn't work. No reaction from the device.

Take out Pin5 and putting a floating wire between the PCB Ground (remember, it is a different ground) that worked earlyier make the device react. The red LED goes of but i still have n invalide answer (but some trafic into the arduino i see).

Then a take of the tape because "it's not shield wire after all" but both upper solution still doesn't work. Could it be that the wire are too longs ? Is it risky to link both Pin5 ground and pcb ground on the SUB9 ? Please note that the multimeter say bip between the Siemens ship up to the arduino pins. 

[AJB2K3]

I'm not sure If I have mentioned this before but I power my interface With a 1500mAh 3 S LIPO battery.

[Toastie]

57 minutes ago, Wapata said:

What are those temperature sensors.

Well, if you browse through Philo's site, you'll find this section: https://www.philohome.com/sensors/tempsensor.htm

It is about how to make your own, but Philo found out which type is actually very close to how the original LEGO temp sensor behaves. I doubt TLG used PT100's or something similar, they tend to go cheap (but rather) reliable. Philo also suggests types of NTCs.

Oh crap - Interface B gone again - that is very bad.

I am just too busy right now with work stuff - it is the second round of exams (you take when the first try, well, somehow "failed". Or you want to improve. Generally, people becoming increasingly nervous  as they have only three tries ... which I hate, exams are good for almost nothing, but that is my very personal view.

I am powering my HC05/TTL2Ser converter also from the Interface B as power source, I need to find that stuff as well ... 

Best wishes,
Thorsten  

[Wapata]

Oh... I did already seen (and forgot) this page 

I'm taking out the ribbon cable right now. I've seen the green 9v led flickering. I don't need doubt so the big replacement is coming.