Bridge position (and other considerations) via S88

[papat400]

Hello, everyone,

I have a few comments to make on the bridge position sent by S88.
I have implemented a turntable management feature in the Desktop Station software, and to improve it, I would like to use everything that the DSD can send via S88 (because it is really very interesting).

Note: my tests were conducted in Mode 2 (DIP SW80) in order to limit the number of S88 modules used.

However, I have noticed the following:

• Contradictory to the description in the manual (see dsd_anleitung_4v5 §6.2.1) , the position of the bridge is transmitted in Hexa and not in BCD. 4810 = 3016 - i.e. 001100002 as shown in Table 4 of the user manual (and as I have observed), whereas 4810 is written as 416 816 in BCD - i.e. 0100 10002.
  It's not a big deal, but perhaps the instructions should be corrected .
• I also noticed that the positions returned by the S88 were in ‘Both sides stop on destination track’ mode. So the only positions provided range from 1 to 24 and never beyond. It will therefore be necessary to use the ‘1st / 2nd half’ bit to determine which side the cab is on, which will complicate processing in Desktop Station a bit.
  Unless it is possible to return the actual position from 1 to 48? I haven't found a way to do this while remaining ‘Märklin compatible’ for the controls.

Thank you very much for your attention.
Kind regards,
Thierry.

[Sven]

Hi,

I just checked, I can not see a problem here. The transmission with 48 positions via the S88 bus works, both DIPs of SW80 must be switched ON (manual table 2). ‘Both sides stop on destination track’ makes no difference here. Please check if your central unit is configured according your S88 Bus length.

I agree to correct the manual about the BCD/HEX description.

Regards
Sven

[papat400]

Hello Sven,
Thank you for your reply.

First of all, I wanted to congratulate you—the turntable works really amazingly with DSD!

To return to my question, here is my detailed reasoning:
I chose to use Mode 2 with DSD because it only uses 24 bits on the S88. For me, this is better than 64 bits as it slows down the bus a little less.
Note: I should point out that I didn't try the other modes to see the difference!

In the manual, Table 4 indicates that position bits are encoded in BCD (in fact, Hexa, thank you for your response as well) in modes 1 and 2. The table suggests that positions are returned from 1 to 48.


However, I have noticed on my network that the S88 only sends values between 1 and 24.
Here are some explanatory pictures:

1) The bridge is located on track 1 (reference track, marked with a red square, the other connected tracks have a gray square). Below the bridge drawing is a text box in which I display various information (for debugging).
The Status Byte (StatusB) and Position Byte (posByte) states as sent by the S88 are shown, surrounded by a red circle.
We can see that bit 2 of the SB is 'true', the Hall sensor is active and we are indeed on track 1. The position is indeed = 0x1.


2) Here it is in position 24:
Status Byte = 0x0, position Byte = 0x18; all is correct.


3) Here it is in position 48:
Status Byte = 0x80, we are clearly in the 2d half, but position byte = 0x18 so it does not send the value 0x30 as I expected.


Of course, it's no big deal, I simply used the “second half” bit to resolve this difference, as I said.

That's how my thinking worked. Did I make a mistake somewhere?
Thank you for your attention.

Kind regards,
Thierry.

[Sven]

Hello,

I tested today and can confirm your error description. I will release revised software in the next few days

Sven

[papat400]

Great thanks Sven !

But for my adaptation in Desktop Station, it doesn't matter. As I said, I simply used the ‘1st/2nd half’ bit of the status byte to do the job, and it works perfectly.

This is what it looks like at present (everything is working fine):


Kind regards,
Thierry.