Wapata

Oh... I was thinking that serial and null modem use 12v for the 1 and 0v for the 0 but the TTL 5v for the 1... Crap, I didn't take a second look on that and I may be wrong

Mine doesn't either. But I am able to put the interface-B in a normal running mode by using the TTL. Soooo I may use an other Arduino mega, a serial monitor and... How do I translate to text ? I guess it should be TTL at the left of the two white square component and serial at the right of them so... Not the same voltages ?

I've found back my oscilloscope ! Look at "dso shell" on google image. It was on the "measurement tools drawer"... how am i supposed to find it here... So for serial communication, if you tell me what to look for, i can trace where the signal get lost (if it is fun for you too ! in the end i already have a working device).

The upper GND as pictured before is the big Ground. I've noted too that someone put a component to make 5v but i thing there is already 5v on the board... in this upper left corner. I have to take a second look to put the Interface-B on Bluetooth One day... After playing with the device... I still have the SUB9 serial port yes. I case i found my mini oscilloscope and can rework on the "where does the signal get lost" part. But I can't "see" if the signal is clean or not. More important : I will use the SUB9 port to "clamp" the final TTL-USB device.

It's a strap So it work with grounds merged (i hope it's okay) ONCE with LEGOInterfaceB. I can click on the Stop button on the device and resume, but i can't click on the Stop button on the computer and resume. We will see what it does with a real TTL-USB thing. Thanks for your support !

Thank you for taking a look. For what is see from dangerous testing here is that the grounding is an issue : if i swap my Rx/Tx wires WITHOUT ground, both Rx/Tx led activate on the arduino. If I put arduino ground to big ground of Interface-B then I can have the red light go off now. If i take back ground to SUB9 ground it doesn't work at all anymore. So the IS something about groundS. ... and it seem it's not wire lenght EDIT By the power of NO fun ! If I disconnect the usb cable and put it back I can make everything work first try with the big Ground and if i do the same with sub9 ground it doesn't work Hurray ? EDIT So it's not cable length. So i cannot use my plan to use the DB9 connector without compromissions now.

Cabling done. Serial null modem communication still one way only from computer to device. TTL still doesn't work. No more 9vLED flickering while moving the board.

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.

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.

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.

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...

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 ;-)

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.

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.

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