[En-Nut-Discussion] TwMasterTransact is blocked

CAMBON, Olivier Olivier.CAMBON at astrium.eads.net
Tue Sep 11 13:34:42 CEST 2012

The call to TwMasterTransact never returns (with or without timeout in
But the CPU is still alive. All the other threads with higher or lower
priorities are alive.

I did not checked the electrical lines with a scope.
But I can see that all the slaves are alive.

Maybe there were some errors during the transaction.
But I think the call should go in timeout in this case.


Olivier CAMBON
ASTRIUM Satellites,
Tests and Products - ASG83 - CZ108
Email : olivier.cambon at astrium.eads.net
Phone : Int.+ 33(0)5 62 19 62 29

-----Original Message-----
From: en-nut-discussion-bounces at egnite.de
[mailto:en-nut-discussion-bounces at egnite.de] On Behalf Of Uwe Bonnes
Sent: Tuesday, September 11, 2012 10:59 AM
To: Ethernut User Chat (English)
Subject: Re: [En-Nut-Discussion] TwMasterTransact is blocked

>>>>> "CAMBON," == CAMBON, Olivier <Olivier.CAMBON at astrium.eads.net>

    CAMBON,> Dear all, I am a new user of the board Ethernut 2.1 ver C
    CAMBON,> Nut/OS 4.10.1.  In my system, the ethernut board drives
    CAMBON,> slave electronic using TWI / I2C bus.

    CAMBON,> I found in the documentation the API TwMasterRegRead and
    CAMBON,> TwMasterRegWrite but it seems that they are not implemented
    CAMBON,> AVR.  So, a wrote my own "i2c_get" and "i2c_set" API.

    CAMBON,> The problem is that sometimes, in the function "i2c_set",
    CAMBON,> call to "TwMasterTransact" is blocked.  I tried with or
    CAMBON,> timeout. The result is the same. The TwMasterTransact does
    CAMBON,> return.

What do you mean with blocked? Does it mean the call to TwMasterTransact
never returns even when given a timeout? That should never happen. Are
sure your hardware works flawless?  Maybe your transaction on the I2C
has some unexpected side effect, disturbing the CPU. Did you check with
scope/logoc analyzer that your transaction does take place and is

Much to check ...

Uwe Bonnes                bon at elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
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