SIM900D Interfacing with hyper terminal.........

[pankaj1984]

sim900 is set to auto baud by factory default,

what i did was to send at+ipr=xxxx baudrate i am using continously until i got the response ok,

hi sir,
i am having same problem. Initially the modem was giving me the delta values and garbage values at 9600 baud, later on at lower baud rate 4800 baud i was able to type 'at' but when i pressed enter the modem is not responding 'ok', i have other sim900 module it is also giving the same output, as per the sim900 serial communication appnote it is mentioned. The delta values that we see are the sync characters that sim900a send to the hyper terminal.
1.> after power on 2-3 sec wait, type 'a' for baud rate sync.
2.> then type 'at' until you get reply 'ok'.(which i am not getting)
i tried to type 'at' almost 50 time but the modem is not responding,
3.> i also tried at+ipr=4800 but its not responding.
The only improvement i have seen is that at lower baud, i am able too type "at" commands in the hyper terminal window.i am using cross cable. And i think its working fine.
Please let me know if anybosy has solution to this problem

 

[sherazi]

Are you typing in CAPS?? you should type AT in caps so that the module detects the baudrate,

 

[pankaj1984]

yes sir I am typing the commands in cap as specified in the data sheet thanks for your reply. regards, pankaj

 

[Graham1904]

yes sir I am typing the commands in cap as specified in the data sheet thanks for your reply. regards, pankaj

Try typing "AT" a couple of times (say 5) and ENTER. The SIM900 should respond with "ERROR" then type AT+IPR=9600 and ENTER. The SIM900 seems to work quite well at auto-baud providing you stick to the rules....

 

[pankaj1984]

Dear Sir,
I have tried "AT" , "AT+IPR=4800", "AT+IPR=?" i TYPED THESE COMMANDS BUT THE MODULE IS NOT RESPONDING. DONT KNOW WHATS THE ISSUE ANY SUGGESTIONS
THANKS FOR YOUR TIME,
REGARDS, PANKAJ

 

[sherazi]

Lets try to debug the complete thing,

first let me know if the network led is blinking slowly or not?

and share your circuit diagram

 

[pankaj1984]

Ok friends At last i have sloved the problem which had troubled me for almost 3 weeks, the core issue was related to power supply, I was using a supply of 10 V 550mA. The SIM works properly at 1 - 1.5 Amp. Second mistake I did was, I used Cross Cable which should never be used for SIM 900A It works On Straight cable. These were the core Issues no the Module is working fine. I would like to brief a few tips for new user of SIM 900A.At low current the module behaves in weird ways it resets gives garbage values.
1.> Use straight cable,2.> use 1-1.5Amp power supply,3.> SIM900A Sends Delta characters when it is turned on for synchronisation.
Thanks For your time and efforts to solve my issue Sherazi, Graham1904 , CKshivarama all the other contributors in the forum.

 

[Echo wang]

Ok friends At last i have sloved the problem which had troubled me for almost 3 weeks, the core issue was related to power supply, I was using a supply of 10 V 550mA. The SIM works properly at 1 - 1.5 Amp. Second mistake I did was, I used Cross Cable which should never be used for SIM 900A It works On Straight cable. These were the core Issues no the Module is working fine. I would like to brief a few tips for new user of SIM 900A.At low current the module behaves in weird ways it resets gives garbage values.
1.> Use straight cable,2.> use 1-1.5Amp power supply,3.> SIM900A Sends Delta characters when it is turned on for synchronisation.
Thanks For your time and efforts to solve my issue Sherazi, Graham1904 , CKshivarama all the other contributors in the forum.

Hi, have you settled it?

 

[Graham1904]

i am using lm317 for power supply...
a quick question... i was checking continuity between antenna pad and ground pad on a new module and i found both of them short(antenna & ground).. is it normal with sim900? can you please verify this?

thanks

LM317 too small for the SIM900 current demand as the requirement is for 2amps for 537uS and so I guess your Vdd is collapsing. Try using 1 x 2200uF cap on the output of the LM317 and this will help ride thro the brown-outs. Any serious change in Vdd will reboot the SIM900....