Garbled serial data (no autobaud?) MTSMC G2 IP

[Thierry Legrain]

I am using a MTSMC G2 IP module connected to a non-5V tolerant processor.
Level shifting is implemented via 5230 ohm in series and 10K ohm pulldown resistors on it’s output lines, particularly on the RX line.
The data I receive is not correct and seems that it’s at the wrong baud rate.

Could level shifter cause the autobaud detection to fail? Can you recommend method for connecting module to 3V only pins?

[Lonny Knudson]

Hi Thierry,
The MTSMC-G2-IP does not support autobaud so you must set your host system’s baudrate to match the MTSMC-G2-IP. The factory default setting is 115200 and this can be changed using the AT+IPR command.
Regarding voltage levels, you should be able to successfully interface the 5V MTSMC-G2-IP with 3.3V host system logic levels. The modem inputs (TXD, RTX, DTR) need to be pulled to >.8V for a logic low, and only need to be driven to 2V for a logic high. The voltage divider you describe on the modem outputs (RXD, CTS, DSR, DCD, RI) looks OK as long as there is no significant load presented by your device. You may want to verify signal levels with a scope to make sure they are within tolerances of the modem hardware and your host system hardware.

• This reply was modified 9 years, 10 months ago by Lonny Knudson.

[Thierry Legrain]

Lonny,

That did it!
Thank you very much for the very helpful and prompt response.
Thierry

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