I2C no Acknowledge hangs module.


Hi everybody,

I am using a Q2686 with 6.61OS and communicate with I2C with several other devices. It work fine. But there is still a problem, if one of the devices didn`t acknowledge, the module hangs. This also occours when the SDA or SCL connection is cut. I need to restart the module, to get in normal operation.

I think, normaly the wathdog must act in this situation, but nothing happens. Even there is no ADL_RET_ERR_BAT_STATE event after the write command, to detect that the slave-device didn`t acknowledge.

Has anybody the same problem, or a solution to nthat problem.

Thanks in advance,




Yes the bug is there. It was in the OS 6.60 also. (In this version the i2c bus api worked only with internal addressing!!!)
I am currently testing OS 6.62 beta, first i thought this issue has been resolved completely but i’m starting to doubt that. The module not hangs this time ( answers for AT commands) but it is sure that part of my application behaves weird. I think it is just the “new constallation of the stars”, nothing specific has been made to resolve this issue.

The only way to remedy this that you write your other devices code and the open at code “perfect”, than it could work. Of course it makes developing very painful.
For example it should be documented that for how long could clock streching enabled before the bus write or read function returns with error. (or not returns ever :slight_smile: )
An external WDT should be implemented in every design , because it is evident that the module internal software WDT can’t resolve every situation.

I’ve heard there are serious issues with SPI bus in OS 6.61 too. It is said to be corrected in OS 6.62 but i have not tested that.




Hi tomalex,

thanks fore your fast reply. I’m going to implemate an external watchdog IC. You say that you a using the beta version of OS6.62. Where i can get this version, or when is this version complete? What does Wavecom say to this Problem?





Ask your disributor for the beta version, but keep it in mind that these versions only for testing and developing don’t expect too much, altough this
beta OS 6.62 and OAT 4.20 looks promising for me, but i don’t use every API.

I rarely contact Wavecom directly and when i do , often i don’t get answers. :confused: