Saturday, June 3, 2017

SIM800 vs. SIM900

Well it actually looks like there are some differences in SIM800 comparing to SIM900. Echo and command routines are working just fine, but reply to SMS send function is different. SMS is actually sent, but the function is not able detect successful sent. There seems to be two reasons. First, the reply looks little different. That is the echo of SMS text is not preceded with empty line and "> ", but there is simply one line with echo. Second, the reply time of SIM800 is significantly slower then SIM900. It looks like "CMGS:#", the acknowledgement of SMS, comes after the SMS is delivered to actual number.

First problem is relatively easy to solve, on beginning we can ask GSM modem for the version and then branch the SMS send function depending on model. But the second must be investigated. I've seen some command that can make difference in how the SMS sending is handled, but the setting in SIM800 looks right already, interesting :).

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