Hot answers tagged

10

After much googling and mashing together various answers, I got it working. Here's the AT command sequence. You can test this from start to finish, you'll just need to confirm the APN of the carrier you're using. // My comments are here Command to send is here Expected responses are here // See if the SIM900 is ready AT ...


6

Without the BGA pads, that's just a QFN package with 1 mm pitch. Yes, you can solder that with a hot air station. The way I usually do this is to use a soldering iron to put a bead of solder on all the pads. Then smear paste flux over everything and position the chip over the pads as accurately as you can. A mag light is handy for this. The paste flux ...


5

Well, that's the recommended circuit. Keep in mind that at the 2uA current draw of the RTC backup, even a 1N4148 will have only about 0.3V drop and it will work down to Vrtc = 2V. A CR2032 lithium primary cell depleted to 2.3V at 2uA is practically dead, so you're not leaving many (micro)joules on the table. Edit: In explanation of the final paragraph ...


5

The GPIOs in sim900 module is meant to be controlled by AT commands through serial port ofcourse. if u see the AT command manual of sim900 you will find the following at command to control the GPIOs AT+SGPIO=<operation>,<GPIO>,<Function>,<level> following is the Description to the above function! P.S. i know this question is ...


4

I'm actually also working on a SIM900 and had the same problem. One possible cause of the problem is that the SIM900 already has made a connection. Try re-starting the sim900 before issuing the commands. Also I set the APN settings with the AT+CSTT= command Below the in/output of my serial connection: For testing purposes use this. Be sure to have the ...


4

I found one way by which escape character can be sent... You do this by specifying the length to AT+CIPSEND command. So the commands exits only after you have sent all data specified by the length... AT+CIPSEND=12 By doing it this way... the escape character can be sent..


4

According to this page, to wake it up, you need to send any AT command, which will be ignored by the module (so no response), followed (within 5 seconds) by AT+CSCLK=0 It took me all of one minute to find that by Googling "SIM800 sleep wake".


4

Ok I finally could get the sleeping current advertised on the datasheet. First, I removed the buck converter and supplied 4V directly to the module so I get better efficiency and removed the supply current needed for the buck converter. That allowed me to strip down a few milliamps, but the true cut down in power consumption was upgrading the module ...


3

You can use electret microphone. Connect its positive to MICP & negative to MIC_N. For speakers, I have used this type of speakers. Connections are same. Alternatively, for testing purpose you can also use your headphone. Cut the headphone wire and you will find wires to connect with SPK_P SPK_N MIC_p MIC_N .


3

For custom client headers use the AT+HTTPPARA command with HTTPParamTag set to USERDATA. It is described in Simcom AT Commands Manual.


3

As @PlasmaHH suggested, changing the text mode to PDU mode (using AT+CMGF=0) did give me some more information. The parsed PDU string now contains a property udh which has some more information about the message. If it's a message consisting out of multiple messages it will tell me how many parts there are and what part this message is of the total message. ...


3

SIM900 Serial interface runs on 2.8 V logic levels, PIC runs on 5 V so you are definitely need level shifting. You did not provide a link to that break-out board but I am sure that there must be some level conversion circuit on that. From application note. Please note that the UART level is 2.8V, if the level is not matching, a level shift circuit is ...


2

Reading through the datasheet I can't see any mention of being able to use the GPIO for sending AT commands and data. I suspect where you've read about using the GPIO for communications they're referring to say attaching a switch which could be viewed as communicating the switch's state to the module. Apart from that there are a number of holes in just ...


2

One way to get current time is by sending a message to itself. Below is an example: AT+CMGF=1 AT+CSCS="GSM" AT+CMGS="0123456789" your phone number THIS IS TEST test message ... ... +CMTI: "SM",1 recevied a message at index:1 ... ... AT+CMGR=1 +CMGR: "REC UNREAD","0123456789","","14/11/15,15:03:13+22" got current time THIS IS TEST Sync your SIM900 ...


2

According to this your Received signal strength is -63dBm. RSSI (=Received signal strength indication). As you say, you can receive RSSI without SIM (SIM IDs you in the network as a user so you can make calls. All the radio capabilities are in the phone, you can check the signal strength without the SIM). For checking the available networks use: AT+COPS=? +...


2

It is actually possible to solder it with a standard soldering station. We used the SIM900 in a project last year, we hand soldered 25~ of them, It worked perfectly fine. Both with soldering wire and soldering paste. I tried to "answer" this as a comment but I dont have enough rep.


2

One problem I can see in your code is the following line: while (mySerial.available() < 0) { The available() method returns the number of characters available and will never be negative, so that means your AT command will never be transmitted, in fact your main code probably isn't starting up. Also you're not terminating the command with a carriage ...


2

The Eagle part you are using is badly designed. The pins are too wide and not centered correctly, and it doesn't have the required routing keep out areas. For the correct dimensions, refer to the SIM900 Hardware Design datasheet figure 38: "recommended PCB decal". The pads should be 1.6mm long and 0.6mm wide, placed 12mm from the center of the part. ...


2

I would take a look at the Taoglas PA.22a chip antenna or the Pulse W3073. They tend to be a little pricey on low quantities, but they are purpose built quad-band (850/900/1800/1900 MHz) antennas that should work with the SIM900 if appropriately designed. A well matched and well designed chip antenna will certainly radiate enough power based on the max-...


2

The problem is resolved. Thanks to @Buck8pe . I removed the c4 capacitor and increased the power supply to 12v so now I am getting loud audio and both of my circuits are working fine with the same supply.


2

It's not impossible, but you have to be very careful from a software point of view regarding the filesystem on the card. Each device must flush buffers and unmount the card before "releasing" it to the other device.


2

It does not really matter for example if you have two slaves beside the MCU or a slave and a turned off other master. So basically the turned off SIM5360 should not cause any trouble to the MCU given it properly unmounted the SD card before turning itself off, just as @pjc50 has mentioned. Disconnecting the lines of the SIM5360 by a multiplexer controlled ...


2

To automate the startup of sim800/sim900 module just keep the pwrkey shorted to ground always. As the supply will be provided modem will be on.


2

The MQTT protocol sits on top of a long-lived TCP/IP connection. There is next to no chance that a cellular modem would maintain a TCP/IP connection while in sleep mode. So you won't wake up from a subscription firing. It's not impossible that once you wake up for some other reason and reconnect, depending on the configuration of the MQTT broker, that you ...


1

As far as I've been able to determine, SIM900 presents a 50 ohm RF output impedance to a load so, if that's right, it behooves you to design an antenna which will present a 50 ohm load to that output, at the frequency of interest. The simplest solution is a vertical whip of some kind, and if you don't know how to determine its length and how to get a ...


1

This is the common problem while taking print out of your design. You have to choose actual size option, instead of fit to size option while taking print out.


1

LM317 is not a good candidate for this project,use LM2576 & LM2596 adjustable voltage regulators check UART level between your host controller(MCU or ...) & Module,if they operate in the different level you need a level shifter buffer. PWR KEY used for turning module ON/OFF,for doing this you must pulled it down for a moment(less than 500 ms or ...


1

The "continuous transmission" requirement cannot be met with regular HTTP requests, you are expected to use every GSM slot, ignoring any higher-level protocols. This test verifies that the emission spectra are within required parameters; this is done by moving a bandpass filter across the spectrum and writing down the power of the signal received. As moving ...


1

The serial connection uses the pins D0 through D3. RX and tX are selectable by jumper on the GPRS module. In addition, you will need ground and power. The GPRS module uses the Vin from the Arduino connector (on the same row of pins as reset, 3V3 and 5V) for power. It also uses the 3V3 to power the LCD. Finally, D5 can be used as a reset on the SIM9000, ...


1

Increase C41, I think. Try double or quad mounting this component to see the effect (you can use the switcher harmonic as a proxy, if you have anything able to measure it). You also need some inductance on the cable side of C42, this will help, particularly if you add another low impedance capacitor across C42. You could also try adding some small ...


Only top voted, non community-wiki answers of a minimum length are eligible