fischertechnik community forum

Very interresting project!
It looks like you are using a BTM-222. AFAIK that module needs AT-commands to configure and connect it. How did you manage to get the RI to send the AT-commands?

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OK,

How do you connect to ftlib, with a BT dongle and a virtual comport (does ftlib/robopro accept that) or with a normal comport and another btm-222?
If I understand you correctly, you suspect that the round-trip time of a request-response cycle is too long.

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Is the performance of this BT module better than of the RF module?
With the TX-C, the latency of the internal BT protocol has a negatif influance on the (semi) real time peformance.

Is someone here fit in Blueooth?

I think we should find out first, what speeds can BT guarantee, aka: Is the whole setup able to hold the 10ms refresh?

BT is a streaming protocol and not developed for (semi) real time use.
This means that the latency is variable as result of the natur of this protocol.
A year ago I measured on the PC-TX-C connection 14 upto 45 ms (95%) and sometimes more.
The USB connection was 10.3 -11 ms 100%.

ISBN:978-0-470-14107-6 pag 163
As rough rule of the thumb is a sample rate of 50 msec for closed loop contol systems with BT.

I could investigate this as I have the BTM222, an IIF, an RI and even TXC and RF data link to compare with. I even have a scope to do delay measurements. At the moment however I'm breaking my .... over another Bluetooth problem so I have very little time. Another thing that I don't have is a BT sniffer. I read on the Internet that Wireshark for Linux has this possibility. I tried to install wireshark on Ubuntu in VirtualBox but dit not manage, basically because I never use Linux and have no clue on how to do these things.

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@Frederic: I'm interested, for the RI the BTM could also replace the RF Module, this would however require a firmware change. If only Knobloch would release the source code

hmm..any idea how it is done with the TX?

Hallo
Ich hätte interesse an dem Layout und der Bestückungsliste um das ganze vielleicht noch für den USB Anschluss zu fertigen denn bei der Seriellen Schnittstelle steht das bei einem Modul immer so weit ab aber mit USB könnte man vielleicht sogar ins Gehäuse rein.

Grüße Olav

Hallo,

@Frederic

Frederic hat geschrieben:... möchte ich gerne von euch wissen ob es überhaupt ein generelles Interesse an dem Modul gibt.

ich wäre sehr an diesem Modul interesiert da ich eine Robo Interface besitze. Ich hatte mir schon überlegt eine RF Data Link zu kaufen, schrekte aber vom Preis zurück!

MfG
Simon

@Frederic

Have you seen this?
http://www.solutron.de/epages/61427429. ... /605000044

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..wow thats expensive