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

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

Reply to
jordi_pn
Loading thread data ...

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
    PC Services
 Click to see the full signature
Reply to
Paul Carpenter

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.