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Problems using uart in H8s. Rx level doesn't down to zero

Started by Unknown January 18, 2007
Hello.
I'm having a problem with a H8S MCU ( 2328) uart I use to comunicate
witch a GSM module.
First I was using a Atmel MCU instead of the H8S and all was working
fine.
But when I have replaced the Atmel with the H8S the communication
dosen't works. I have seen thant the problem is that when the GSM
module tries to respond to the H8s,  the  signal level  ( H8S-Rx )
doesn't reach to zero ( it only downs to 1,5 volts, so you can see the
byte modulation between 5V and 1,5 ).
how can it be if the only  difference is the MCU? A diferent input
impedance? A firmware configuration?


Thank you

On 18 Jan, in article
     <1169131366.507048.271420@q2g2000cwa.googlegroups.com>
     jordi_pn@yahoo.es wrote:

>Hello. >I'm having a problem with a H8S MCU ( 2328) uart I use to comunicate >witch a GSM module. >First I was using a Atmel MCU instead of the H8S and all was working >fine. >But when I have replaced the Atmel with the H8S the communication >dosen't works. I have seen thant the problem is that when the GSM >module tries to respond to the H8s, the signal level ( H8S-Rx ) >doesn't reach to zero ( it only downs to 1,5 volts, so you can see the >byte modulation between 5V and 1,5 ). >how can it be if the only difference is the MCU? A diferent input >impedance? A firmware configuration?
I very much doubt the ONLY difference is the MCU as I doubt you have a pin compatible MCU between Atmel and Renesas H8S. Somewhere on your new board you have something wrong as we do not know if this is a board of your own design or bought in module, we can only make assumptions. This actually sounds like bad connections, on the serial data and possibly even broken ground/0V between the H8S and GSM module, which may well be using a different connector at H8S than the Atmel (as we have no way of knowing). The other thing to check VISUALLY and with meter is all the power and ground pins on the H8S are actually connected. Testing with a meter will not tell you if a ground pin is actually soldered correctly, as it will find a path through the device. We also have no idea what is between the GSM and H8S in the way of connectors buffers, level translators, devices operating at different voltages, etc, etc, etc,..... -- Paul Carpenter | paul@pcserviceselectronics.co.uk <http://www.pcserviceselectronics.co.uk/> PC Services <http://www.gnuh8.org.uk/> GNU H8 & mailing list info <http://www.badweb.org.uk/> For those web sites you hate