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