Interfacing GSM modem with 80s52 | Microcontroller › 8051 › Interfacing GSM modem with 80s52 This topic has 1 reply, 2 voices, and was last updated 11 years, 6 months ago by RUBEN KURIAKOSE. Viewing 2 posts - 1 through 2 (of 2 total) Author Posts March 7, 2013 at 9:56 am #2168 prajwalParticipant hi, I have a gsm modem named WISMO. I tested the modem with PC and its working fine. When i tested with PC I DID NOT USE MAX 232. Now i need to interface it to the controller should i use max232?? Pls help April 13, 2013 at 10:33 am #9483 RUBEN KURIAKOSEParticipant when ever you are trying to interface a TTL device with a CMOS use aMAX 232 between them since there requires a voltage change over. Author Posts Viewing 2 posts - 1 through 2 (of 2 total) You must be logged in to reply to this topic. Log In Username: Password: Keep me signed in Log In