Is it realistic to put the following: GPS module, GSM module, SD card slot and about 4 analog sensors into Arduino uno? (have not yet goten an Arduino in my hands).

  • \$\begingroup\$ Find the datasheets for the different modules you want to use and the Arduino and add them to your question. Next find out from the datasheet which pins and interfaces are used for each shield. The short answer will be that you'll have a challange connecting them all at the same time, as many shields use the same pins by default, but I'm not saying it can't be done. In fact, in a case like this it makes more sense to use generic modules than to use proper Arduino shields, because you'll probably run into pin conflicts anyway. \$\endgroup\$
    – jippie
    Mar 2, 2013 at 16:29
  • \$\begingroup\$ I have consulted, in prior exchange article just this. Where GPS and GSM shield used the same pins. The solution was bend the pins away when stacking so not to connect and use jumper wires, and redefine the pins in the code to what was jumped. \$\endgroup\$
    – mpflaga
    Mar 2, 2013 at 17:46

1 Answer 1


How many functions? That depends on a few factors. First, will I have enough pins? The GPS module will probably take up two PWM pins (Rx and Tx) but I recommend you hook the Rx and Tx of the GPS directly into the hardware serial Rx and Tx of the Uno. The senors will probably use a single analog pin each. The Arduino Uno has six. I'm not sure how many pins the GSM module will take up but you have at least 3 PWM pins left to fool around with. The SD card, from my understanding, can be hooked up directly to the Uno using SPI and the ICSP pins. I'm not certain of this, so it's probably worth doing some more research on. The SD card will require at least 2 PWM pins if you're not able to use ICSP.

Second, will I have enough RAM and flash memory? As soon as you start doing lots of stuff on the Uno you realize that 2KB of RAM and 31.5KB of flash memory isn't a lot. The Arduino IDE will tell you if your sketch is too big to fit on the Uno when you compile it, so draw up a quick sketch that has all the library/function calls you need and go from there.

Third, will I have enough serials? I've only been able to get two serial connections working on the Uno (but I've been told you can get three working with some hassling). That is the hardware serial (accessed by the Serial object) and a SoftwareSerial object. The GPS will definitely utilize one of these and I bet your GSM module will use the other. Don't forget about debugging! Since you won't be able to have all three of these hooked up to your Uno I recommended debugging with the GSM module. Get this working and then move all your debugging code from Serial to your GSM connection. That way instead of using the Serial output on your computer you'll have to read from wherever your GSM module is sending data to.

  • \$\begingroup\$ Wow, great answer, thank you, just I am new in arduino, need some time to understand it all. What about arduino mega? It has a 8 KB RAM and 248 KB flash memory, more pins and serials. \$\endgroup\$
    – Alej
    Mar 2, 2013 at 21:54
  • \$\begingroup\$ @Alej An Arduino Mega has just about more of everything (except for clock speed) and should definitely work here. If you don't mind paying a little extra it's a good choice. If this answers your question please click the "check" next to it. \$\endgroup\$
    – Kevin Mark
    Mar 2, 2013 at 22:21

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