Project: Programs to allow interactions between old Lego Control Interfaces (RCX, Lego Interface B, others?)

[Toastie]

@Bliss

WOW!!!

This is more than I and surely others were hoping for! With these additions, LEGO Blocky becomes the most powerful programming language for the Interface B running blistering fast - on modern machines - and platform independent! Crazy. I will be in Northern Germany the next week, but will have the interface B, an RCX with me for testing. I am pretty sure that everything will work perfectly well!

Sensing and turning outputs on/off in response is one thing. Having a full-blown, multitasking language in between is something totally different.

This is so unbelievably nice!!!

All the best
Thorsten 

EDIT: And there is "Yield" - so nice! This actually makes code look pretty. I have such a procedure on all my VB6 programs: Yield to other processes ... 

 

Edited Wednesday at 06:56 PM by Toastie

[Toastie]

OK, I did some more Blockly code testing, as it is right now (last version, @Bliss published).

If I understand this entire Interface B/LEGO Blockly combo correctly, we are experiencing the birth of a new power house for LEGO programming in real time. There is the I/O module and the brain.

The I/O module, Interface B, has 8(!) sensor inputs serving the original 9V LEGO Mindstorms sensors - and of course the entire suite of either third party or homebrew sensors of this system. And it features 8 9V PWM controlled outputs. 

The brain is a modern - and thus in every regard superfast computer, as compared to 1993, when Interface B was introduced. Code on the brain thus runs incredibly fast. 

The link between brain and interface is serial, with hardware supported sensor data encoding on the interface side (raw, touch, clicks, °C/°F, rotation count encoding), running at 9600 baud; which is - I believe - the "reaction time" bottleneck, but this is a fixed given.

As far as I am concerned, this is one of the most attractive LEGO vintage HW / modern SW combo I ever worked with.

Here is the thing: With a fast serial to parallel converter, speeding up the serial link to HW limits, whatever it is today, there is - again as far as I know - no reason not to use Interface A with LEGO Blockly. And that would be a killer application.

Interface A only knows outputs turned fully on/off, but I wonder if is possible, to do PWM as it is done in TC Logo: An interrupt service routine (=task in LEGO Blockly), called every 1 ms to update the 6 PWM outputs on Interface A/read the 2 inputs, and in between, operational code is executed on the computer. That would be another milestone for vintage LEGO HW control.

All the best,
Thorsten

[Bliss]

Lego Blockly Current version 2026-04-01-1836.

I did some automatic task naming and rename, delete etc managements etc...

 

If I find an Interface "A" 9750 one day, I'm sure I will enjoy very much to integrate this to blockly...
But I don't expect this to happen anytime soon.
We don't see this often on marketplace...  It's rare and expensive on bricklinks...

[Toastie]

13 hours ago, Bliss said:

I'm sure I will enjoy very much to integrate this to blockly...

@Bliss

This is again wonderful news!!!

I also believe that you really don't need an Interface A for experimentation, as you would need a serial to parallel converter anyway, and all modern computers/laptops etc. don't have that anymore (since long).

Such a converter can be the smallest Arduino or the like microcontroller with 8 I/O ports and two more for an USB2TTL (or BT2TTL) adapter. The little bit-banging code I wrote some time ago as well as the corresponding interface is here:

https://www.eurobricks.com/forum/forums/topic/192941-lego-interface-a-97509771-–-lego-technic-control-1-tc1-referenceideas-thread/page/3/#findComment-3586230

@maehw has modified the code a bit (I am a chemist ^^) to make it even better.

With such an interface no 9750 is required at all, as you can see the LEDs of the Arduino flashing as they would exactly on the Interface A. The latter is nothing more than a "motor driver" (6 outputs). In addition, it provides permanently sensor data, converted to TTL on/off level. Whatever you write as 6 bit (0-5) word (e.g., 111111 for all outputs on, or 100000 for output 5 on and outputs 0-4 off) to the 9750 TTL compatible inputs at any time, is directly funneled to the motor output. Whenever you read the status of 9750, you'll get back an 8 bit word, bits 0-5 = output status, bits 6+7 = sensore status (= on/offm, there is no ADC or something like that inside 9750.

The software for 9750 (within the LEGO DACTA Technic Control 4.5V universe) does either build on simple output on/off schemes (as well as input is on or off). This holds true for 4.5V touch sensors or 4.5V >light change< sensors. As said, there is no A/D.

There is - as far as I know - one exception (@evank and @alexGS know better!) and that is the TC Logo for DOS (and maybe Apple?), which provides PWM control for all 6 outputs. Here is how they did that (sorry for the long read):

https://www.eurobricks.com/forum/forums/topic/192941-lego-interface-a-97509771-–-lego-technic-control-1-tc1-referenceideas-thread/page/3/#findComment-3586230

In essence, every 1 ms, a 6 bit word, representing the current PWM state of all 6 outputs (either on or off) is sent to 9750. A full PWM cycle is 8 words, so that the full PWM signature for power settings between 0 and 7 takes 8 ms = 125 Hz. The signature is adjusted to the characteristics of 4.5V motors, I believe. Upon changing power level of one or more outputs, only the 8 variables are changed. Here is a QBasic program, which is way too slow, but shows the idea:

'Program PWM_1.BAS (2023-4-20)
'Simulation of the TC Logo PWM routine => WritePowerOutByte
'In TC Logo, WritePowerOutByte is called every ms by timer interrupt (8)

DEFINT A-Z

DECLARE SUB WritePowerOutByte (i AS INTEGER) 'Write 8 bit long PowerOut array to
                                             'serial port COM1.
DECLARE SUB CalculatePowerOut ()             'Called every time the user changes a
                                             'power setting for a 9750 chn.
'Constants
DIM SHARED PWMData(0 TO 7) AS INTEGER        'Array with the (const) 8 pwm settings.

'Variables
DIM SHARED UserPower(0 TO 5) AS INTEGER      'User power settings (0-5)
DIM SHARED PowerPWM(0 TO 5) AS INTEGER       'Calculated from PWMData and UserPower.
DIM SHARED PowerOut(0 TO 7) AS INTEGER       '

DIM t AS DOUBLE                              'For performance checking only.

'============================================================================
'Setup
'
'Prepare (const) pwmdata-power (0-7) array.
'Data arranged as in TCLogo; 
'              'MSB         LSB
'DATA 0        '0 0 0 0 0 0 0 0        'Always off = pwr 0
'DATA 17       '0 0 0 1 0 0 0 1        '             pwr 1
'DATA 73       '0 1 0 0 1 0 0 1        '             pwr 2
'DATA 170      '1 0 1 0 1 0 1 0        '             pwr 3
'DATA 214      '1 1 0 1 0 1 1 0        '             pwr 4
'DATA 238      '1 1 1 0 1 1 1 0        '             pwr 5
'DATA 254      '1 1 1 1 1 1 1 0        '             pwr 6
'DATA 255      '1 1 1 1 1 1 1 1        'Always on =  pwr 7
DATA 0, 17, 73, 170, 214, 238, 254, 255

FOR n% = 0 TO 7: READ PWMData(n%): NEXT n%

'power(n) = array with the actual power data (0-7) of each channel 1-6.
'Every ms, each column is sent via the OUT command to 9750.
'Power 0-7 need to be translated using pwmdata array:
'
'      Example only: ' MSB                LSB
UserPower(0) = 7     ' 1  1  1  1  1  1  1  1 'PWM LSB = ouput 1
UserPower(1) = 6     ' 1  1  1  1  1  1  1  0
UserPower(2) = 5     ' 1  1  1  0  1  1  1  0 'PWM bit structure of output 1-6;
UserPower(3) = 4     ' 1  1  0  1  0  1  1  0 'as determined by measurement.
UserPower(4) = 3     ' 1  0  1  0  1  0  1  0
UserPower(5) = 1     ' 1  0  0  0  1  0  0  0 'PWM MSB = output 6
'                    ------------------------
'           pwm byte: 63 15 23 11 55 15  4 31 '"Added column" result = PWM output.

'============================================================================

CLS
CALL CalculatePowerOut
PRINT "Running"

't = TIMER

DO                                   'Each call = timer interrupt.
  FOR i = 0 TO 7                     'One cycle = 8 bits
    CALL WritePowerOutByte(i)
  NEXT i
LOOP

'PRINT USING "#.##"; (TIMER - t)

SUB CalculatePowerOut
  powerbit = 1
  FOR PowerOutBit = 0 TO 7
    pwmbit = 1
    FOR chn = 0 TO 5   
      temppower = PWMData(UserPower(chn)) \ powerbit
      temppower = temppower AND 1
      temppower = temppower * pwmbit
      PowerOut(PowerOutBit) = PowerOut(PowerOutBit) + temppower 
      pwmbit = 2 * pwmbit
    NEXT chn
    powerbit = powerbit * 2
  NEXT PowerOutBit
END SUB

SUB WritePowerOutByte (i AS INTEGER) 
  OUT &H3F8, PowerOut(i)  '&H3F8 = I/O address for serail port (COM1)
END SUB

Do you think it is feasible to create a LEGO Blockly block that just does this: 1 ms repetition time, crank out a byte (only 6 bits used) and immediately read back a byte (status including sensor ports), and power setting blocks for one or multiple outputs? The thing is, on TC Logo that I am running on an IBM XT or the DOSBox-X emulator, 9600 baud is the max baud rate for COM ports (without tricks). For the modern PC/laptop Arduino based serial2parallel conversion, way higher baud rates are possible, so that the 1 ms rep rate is not an issue at all. It is a little on the IBM, as 9600 baud, 8N1 need slightly more time than 1 ms to transmit.

This would be so cool!

I regard LEGO Blockly as powerful and fast programming environment to drive outputs (Interface A+B, and to some extent Control Center I/II), read inputs, and process the data to do something. RCX and the like want to be programmed and then do stuff on their own, but can be regarded as output drivers and sensor data providers as well. The processing of these data are done on the RCX (etc.) though. That is not the case for Interfaces A+B.  They require a brain :D

All the best
Thorsten

   

Edited yesterday at 12:28 PM by Toastie

[Bliss]

@Toastie,

I would certainly not recommand to do any time critical (1ms serial commands to achieve some sort of PWM) logic into a PWA (Progressive Web Application) like my blockly app is.

Since we do not have to comply to TCLogo standard, I would rather recommand to do the PWM logic into the Arduino!  An arduino is needed anyway and would be a lot more precise and smooth I think...
The Blockly would then use commands as it does to interface B.  Out 1 Pwr 7 (0 to 7).

Even better, we could try to make a Arduino sketch to simulate Interface B behavior, so we could use the same protocol for both. 
That would require No change to do in Lego Blockly as it would think it connects to an Interface B.  (Or we could think of another init statement as the "Do you byte" of int.B ot identify it's actually Int.A...)
Maybe this already has been done?

The simulator would have to create a 19 bytes packet stream with checksum byte, that would be used to get the 2 inbut status of interface A...
There are 8 inputs to Int.B, so could use Input 1 and 2 for Int.A input status, and Input 3 to 8 for Int.A Out 1 to 6 Status.  Could also be inp 1 to 6 for Int.A out 1 to 6, Inp. 7, 8 for Int.A Inp Status...

Having a Lego Interface B simulator for Arduino, ESP32 etc, would allow to use the Lego Blockly for custom arduino projects!

That gives ideas to create "Proxys" or Gateway like you did with the PBricks...  But for non smart devices like Int.A and Int.B...  and other Arduino projects...

I wanted to implement MQTT to Lego Blockly but since i'm using HTTPS which is secure, it become complicated with MQTT and I abandonned the project for now...
But the idea of a Serial Gateway,  like serial comm with ESP32 that would achieve some MQTT client stuff, why not.
And Why not use the Int.B protocol haha...  Nothing to do in the blockly interface...  :-)

Anyway, for Interface A.  Making the PWM logic on arduino should not be that complicated and probably already done somewhere...
As for making a Lego Int.B simulator, that would be a fun project.

Edited 22 hours ago by Bliss

[Wapata]

Hi !

Does it work with cybermaster on Lego 8482 ?

[Bliss]

1 hour ago, Wapata said:

Hi !

Does it work with cybermaster on Lego 8482 ?

Not at the moment,  I guess it should not be that difficult to achieve though as they share many common points.

For now I did only support for devices I own, like RCX and Interface B.

Now I also own Lego WeDo and Boost stuff and also an EV3 but did not yet play with those :-)

 

Edited 21 hours ago by Bliss

[Wapata]

Oh crap... I've opened my 8482 set too early then.

Mmmff I have to go find my win 98 old computer now 

[amine]

I am curious if there is a way today to program a microcontroller like arduino or microbit using the old Logo instead of C ?

[Bliss]

38 minutes ago, Wapata said:

Oh crap... I've opened my 8482 set too early then.

Mmmff I have to go find my win 98 old computer now 

Why would you do that, what about Bricxcc. (https://github.com/BrickBot/BricxCC/releases/tag/v3.3.8.9)

My lego blockly app only sends simple communication commands.  It does not download any programs into these PBricks.

If you just want to send commands to turn on/off motors you may try to use my blockly app who knows, it might work.  Try it. (You need to download a firmware into you cybermaster brick first if not done already).
I know I do not have all special commands decicated to Cybermaster but some basic command might work...
I may check what are the differences and maybe I just need to had few blocks...

 

Edited 21 hours ago by Bliss

[Wapata]

 thank you for the link 

[evank]

18 hours ago, Bliss said:

Lego Blockly Current version 2026-04-01-1836.

I did some automatic task naming and rename, delete etc managements etc...

 

If I find an Interface "A" 9750 one day, I'm sure I will enjoy very much to integrate this to blockly...
But I don't expect this to happen anytime soon.
We don't see this often on marketplace...  It's rare and expensive on bricklinks...

I have several and would be happy to donate one to you, for the cost of shipping from the US.

5 hours ago, Toastie said:

There is - as far as I know - one exception (@evank and @alexGS know better!) and that is the TC Logo for DOS (and maybe Apple?)

Yes. Lego LOGO for the Apple II was probably the most common version here. You can use the SETPOWER command to control motor speed. I wish there was an easy way to do that in BASIC, which everyone knows is my preferred language. I'm not writing assembly code.

[Toastie]

2 hours ago, Bliss said:

Anyway, for Interface A.  Making the PWM logic on arduino should not be that complicated and probably already done somewhere...
As for making a Lego Int.B simulator, that would be a fun project.

He-he - this is getting fascinating - having the HW/SW simulators (Arduino etc. based) would really be fun, as you need not have the expensive vintage equipment, could develop cool programs try them out, see what they can accomplish. And then eventually reconsider your saving/buying habits.

Yes, I did implement PWM control for 4.5V LEGO as well as Tenka's cubic motors using an ESP Vroom board with some H-bridge breakout board drivers for my suspended train:

https://www.eurobricks.com/forum/forums/topic/197590-mod-85007-pantasy-suspended-steam-punk-train-motorized-with-tenka’s-circuit-cubes-elements/#findComment-3687247

The ESP's have so many PWM options, it is crazy. And as you said, your Blocky code then needs to manipulate only the PWM controls ...   

Best regards,
Thorsten

[Bliss]

@evank, thank you very much for the offer, you are very generous man!

Actually, I have an arduino uno, and wired LEDs using the PWM pins...   I think it might do the job for testing...
So I might not need the real thing for now.  But again thank you! 

 

@Toastie

So I wired up my Arduino uno and I found the following website that you guys may know about?
https://wiki.lvl1.org/Lego_Interactive_Interface-A_Driven_via_Arduino

I used the arduino code that you can find on this web site and put it into my arduino.
I wired my FTDI USB to TTL to the Input 0, 1 of the Uno and used Termite to send the Commands like PORT 0 ON, COMBO B LEFT, PWM 1 128 etc and it is working but slow.
(I wired 6 LEDs on the pwm ports 3,5,6,9,10,11)
I added the Serial.setTimeout(50); to the main sketch and it's fast now.

I can do something using this protocol (sending text command and get text replies etc) and could provide the sketch for Arduino Uno in my Github.  You coud then adapt the code for an ESP32 for example or other boards...

I also tried a simple Sketch I found in one of your post @Toastie that is not doing the PWM but it is working too somehow.  And you have the feedback of the output status in addition to inputs.
Are you doing something with these output status?
Because the code I found on LVL1 does not seem to use this port manipulation hack and before I try to integrate this to their code, I want to make sure there is a real Gain. 

Unless you guys suggest otherwise, I'm going to use the LVL1 arduino sketch as a base to do testing and I will use their commands protocol (they already made a command parser).

 

When I have something done in my blockly for Int.A, I will need testers that have the real Int A box :-)

Edited 14 hours ago by Bliss

[evank]

What if I insist on sending it to you? :) I have more than I need and your project is a great cause.

Selfishly, I really want to see your software work on the real hardware.

Otherwise I look forward to testing it myself, but I'll probably need some hand-holding.

Edited 13 hours ago by evank

[Toastie]

10 hours ago, Bliss said:

Are you doing something with these output status?

Not me, but yes :D

Upon program startup, the original LEGO TC Logo software, as well as the LEGO Lines program and other (for the BBC Micro and so on), do send 0x63 (or any 6 bit pattern) and then immediately reads back the I/O port status. As the Interface cards for the IBM (and others) have latched I/O ports (74LS373, VIAs, PIOs etc.), the value sent out is read back from the 9771 (etc. card). It does that on the IBM at two I/O addresses. If there is no or wrong read back value, the LEGO software assumes there is no such card present and refuses to work. It can't check for the Interface to be present.

As I am using an original 9771/9750 combo and the original software on an IBM as well as on DOSBox-X (serial version of TC Logo made by @alexGS) I needed to mimic that behavior for the latter. This way I can do TC Logo/QBasic programming on my laptop with just the Arduino attached.

Best,
Thorsten

P.S.: Yes I knew that website, but I wanted something simple and fast ;)     

Edited 5 hours ago by Toastie

[evank]

They even suggested similar code when using BASIC. I ignore that part, since I'm not in school :) and already know where I slotted the Lego card(s).

[Bliss]

@Toastie,

But for now, since we are not relying on TC Logo etc, and we want the PWM taken care on the arduino, I will use the LVL1 arduino sketch with a small modif to make it faster and I will not implement any output status for a first draft.
If it is really needed, I could put some effort to implement this in the future.

The LVL1 arduino sketch had a 1sec delay because they used "Serial.readString()" rather than Serial.readStringUntil('\n').  (Note the use of delimiters).
Without delimiters, there is timeout of 1sec automatically...  (unless you use serial.setTimeout(20) for 20ms...  But they did not...  Anyway, the fastest is to use readStringUntil with a delimiter.

They use textual commands rather than bytes command, and they use a string parser.  It is not the fastest but it is very intuitive so I keep it that way for now...
I implemented the comm already and it looks promising.
I will implement the blockly blocks for this today so you will have something to test very soon.
 

Please folks, find the folder of the sketch for the Arduino Uno here:  https://github.com/BlissCA/lego-blockly/tree/main/SketchArduino/Lego9750

The wiring must respect the following table taken from LVL1 site:

Wiring

Arduino	Brick	Port Id
3	6	0
5	8	1
6	10	2
9	12	3
10	14	4
11	16	5
A0	18	6
A1	20	7

Also, I used a simple USB to TTL FTDI where FTDI Tx gos on Arduino pin 0 Rx, and FTDI Rx goes to Arduino pin 1 Tx.  FTDI GND goes to Arduino GND.