| ??? 09/21/04 12:41 Read: times |
#77812 - RE: Inerfacing External modem to 89C52 Responding to: ???'s previous message |
Have you used a proper RS232 Transceiver?
(eg, MAX232) kunal subhash patil said:
The baud rate i am trying to achieve is 115200 Why? That's fast for an 8051 (not necessarily impossible, but non-trivial) kunal subhash patil said:
i've used the polling method for transmitting and receiving the character. Definitely a bad idea for receiving at 115200!!! You need an interrupt-driven receiver - especially without hardware flow control! Also, remember that no analog phone line modem can receive at even 56k, and transmission is limited to ~36k: http://www.8052.com/forum/read.phtml?id=75995 kunal subhash patil said:
When MC connected to the COM port i can very well see 'AT' displayed on the hyperterminal provided i am communicating at 9600. But the same program fails to display 'AT' at any baud rate higher than 9600. So, your code doesn't work above 9600. But, is there any need to go above 9600: http://www.8052.com/forum/read.phtml?id=76147 kunal subhash patil said:
Now the 2nd problem is of getting an 'OK' response. Even if i am able to send 'AT' to the modem ( which i can easily verify by communicating with COM port of PC ) i am not able to receive 'OK' response Have you enabled the receiver? Have you checked this with hypoterminal? kunal subhash patil said:
Also if i try to dial the modem by command 'ATDP215' ( 215 being the extension no. ) i don't get any carrier detect signal or no dialing tone can be heard. Does the modem work when connected to hypoterminal? |
