7 Replies Latest reply: Oct 24, 2014 1:59 AM by Harald Naumann RSS

Help with GL865 QUAD serial communication




     I'm developing a GPS tracking with two Telit's modules and a Cortex-M4 processor. The module I've been using is a Jupiter JN3 and a GL865 QUAD. I'm not using any development kits, mainly because this is gonna be my graduation presentation.

     So here's the deal, I managed the GPS module to work properly, it sends me the NMEA sentences with the frequency I desired, but the GL865 has been showing me a funny behaviour.

     I power the module and the power monitor sends me 2.8V, as expected. The RXD and TXD pins, at first, was working fine and responding to my AT commands, which are sent from the processor. Now it stopped working to any of my commands. I put a scope on the RXD and TXD and it shows me almost a square waveform for a few seconds and then both outputs are going low. Sometimes, I turn on the module and these outputs are constantly high.

     I've sent a lot of commands trying to make it work and no response. My thoughts are that the module is going to some kind of sleep state, but the wake commands doesn't work too.

     I made some measures and it shows me that the VBATT is short-circuited to GND such as the antenna. I think the antenna is fine, there must be some kind of internal high frequency filter, but the VBATT concerns me.

     Has anynone experienced the problem, Any ideas? I can send the schematics and the waveform if neede.