Question

Hello.

I have one iButton permanently connected to 1 wire on FMB 122 and I/O for iButton configured to High / "On change". In this case I can see this permanent iButton code in every message which is sent by FMB device.

Problem occurs when I have another iButton reader connected to same 1 wire bus. There are 2 scenarios dependent on specific iButton used:

1) I use iButton by reader and this overwrites field "iButton" in message, DOUT2 is activated, buzzer beeps and this new iButton code is send by FMB device in one message and after detatching it from reader, permament iButton starts to send its code again. This is desired functionality.

2) I use iButton by reader and nothing happens. There is no change in message, no iButton detection (no buzzer on DOUT2). Permanent iButton on 1wire is not overwritten.

I'm using original iButtons, no China copies. For some of them desired functionality works perfectly. For some of them scenario 2 is achieved, which is not desired.

Please, any tips on how to achieve scenario 1 everytime on FMB 122? How FMB 122 choose which iButton to send while there are 2 of them connected to 1 wire bus. What can be potential reason that one iButton can overwrite permament one, and another one is not?
 

FMB 122 Firmware: 3.18.20

Thank you,

Peter

Comments

After research I have another insight in this problem.

When 2 iButtons connected to 1 wire bus, FMB 122 chooses only one regarding iButton code which is sent in message (higher iButton code wins). I think this is issue in Teltonika FMB 122 firmware and 1 wire master implementation and search algorithm which get only iButton with highest iButton code value. My opinion is that proper way to not to loose any of iButtons connected to 1wire bus is to check which iButtons are connected to bus and send them one by one in multiple messages.

Please, can anybody from Teltonika confirm or reject my theory?

Thanks, Peter

Answer 1

Hello,

Could you explain why you need two readers attached to one FMB122 device ? What exactly you trying to achieve by that ?

Comments

I have one reader for vehicle driver (not permanent one) and second reader for vehicle equipment which is attached permanently to 1 wire bus after connecting vehicle equipment.

I think, this scenario is valid regarding 1 wire bus functionality. My question is, how it is possible that for some iButtons they are able to overwrite permanent iButton connected to bus after using vehicle driver reader, and for some iButtons they are not.

Peter

---

After research I have another insight in this problem.

When 2 iButtons connected to 1 wire bus, FMB 122 chooses only one regarding iButton code which is sent in message (higher iButton code wins). I think this is issue in Teltonika FMB 122 firmware and 1 wire master implementation and search algorithm which get only iButton with highest iButton code value. My opinion is that proper way to not to loose any of iButtons connected to 1wire bus is to check which iButtons are connected to bus and send them one by one in multiple messages.

Please, can anybody from Teltonika confirm or reject my theory?

Thanks, Peter