Ring, Ring! Who’s that callin’? It’s your breadboard! Introducing Adafruit FONA MiniGSM, an adorable all-in-one cellular phone module that lets you add voice, text, SMS and data to your project in an adorable little package.
This module measure only 1.75″x1.25″ but packs a surprising amount of technology into it’s little frame. At the heart is a GSM cellular module (we use the latest SIM800) the size of a postage stamp. This module can do just about everything
- Quad-band 850/900/1800/1900MHz – connect onto any global GSM network with any 2G SIM (in the USA, T-Mobile is suggested)
- Make and receive voice calls using a headset OR an external 8Ω speaker + electret microphone
- Send and receive SMS messages
- Send and receive GPRS data (TCP/IP, HTTP, etc.)
- Scan and receive FM radio broadcasts (yeah, we don’t exactly know why this was included but it works really well)
- PWM/Buzzer vibrational motor control
- AT command interface with “auto baud” detection
- Onboard LiPoly battery charging circuitry so you can take your project on the go. Use any 500mAh+ LiPoly or LiIon battery and recharge over the MicroUSB when necessary. Two LEDs let you know when its charging and done
- Standard 4-pole TRRS headphone jack. Use any ‘Android’ or ‘iPhone’-compatible headset with mic
- Breakouts for external 8Ω speaker and electret mic if you don’t want to use a headphone
- Level shifting circuitry so you can run it with 2.8V to 5V logic.
- Vibrational motor (buzzer) driver so you can have noiseless notifications
- uFL or SMA connections for external antenna
- Indicator LEDs for power and network connectivity
- Standard SIM slides into the back
You will also need some required accessories to make FONA work. These are not included!
- SIM Card! A 2G Mini SIM card is required to do anything on the cellular network. US AT&T no longer sells 2G SIMs and will shut off their 2G network, so for American customers we recommend any T-Mobile or reseller (SIMPLE mobile, etc) that uses the T-Mobile network.
- Lipoly Battery – 500mAh or larger! This 500mAh battery, or this 1200mAh will work great.
- MicroUSB cable for charging the battery.
- External Antenna – this straight one or this right-angle one will work well.
- If you have the FONA with uFL connector – a uFL to SMA adapter cable.
- TRRS 4-Pole Headset – Any ‘iPhone’ or ‘Android’ compatible (but not iPhone original) should work. We tried about 10 different ones, and basically the more expensive once are more comfortable and louder but our official iPhone headset mic did not work.
- External Mic & Speaker – If you want to talk directly to your FONA, an electret mic and mini 8 ohm speaker will do quite nicely.
- Vibrating motor – the FONA can drive this directly, just solder a mini vibrating motor disc in!
- USB console cable – the microUSB connector is for charging only, but you can wire up a console cable for direct-connection to the module if you want to send commands from a terminal (great for testing and tweaking)
There’s three external connectors along the left side, from the top, a mini JST 2-pin, a microUSB and a headphone jack.
- JST 2-pin – this is the battery input connector. It works with any of our Lipoly batteries but since the charge rate is 500mA (and the cellular module can spike high current draw!) we suggest our 500mAh or 1200mAh batteries. You can also connect a JST cable here if you have other plans.
- MicroUSB connector – this is the LiPoly/LiIon battery charging port. The SIM800 has a USB interface but its ONLY for reprogramming the module with an expensive and unavailable IDE. So charge only! The charge rate is 500mA max.
- Headset jack – this is a ‘standard’ TRRS 3.5mm phone headset jack with stereo earphone and mono microphone. Any ‘iPhone’ or ‘Android’ compatible (but not iPhone original) should work. We tried about 10 different ones, and basically the more expensive once are more comfortable and louder but our official iPhone headset mic did not work for unknown reasons. Sleeve is Mic+, first ring is ground, then the second ring and tip are for stereo audio. The module does not have stereo out so we just tied both together.
Up top is the place where you can plug in your antenna. An antenna is required to use the module for any kind of voice or data communications as well as some SIM commands!
We have both SMA and uFL versions. The uFL version is good if you want to connect the antenna to the outside of a box or route it around. If you are using the uFL version you will probably also need a uFL to SMA adapter cable.
If you have an SMA version, you can connect an antenna directly. We suggest a quad band GSM/GPRS antenna, but if you’re savvy and know what frequencies are used in your area you can get a single or dual band antenna that’s just for your required frequency
SIM Connector (on Back)
A 2G Mini SIM card is required to use the module. Nearly any cell phone shop can sell you a SIM card. It must be a 2G GSM card. AT&T in the US does not sell these anymore! They are shutting down their GSM network, and only T-mobile sells and supports a GSM network. If you are in another country, chances are you can just ask for a GSM 2G card.
MicroSIMs won’t fit – so make sure its a “Mini” SIM.
Mini SIMs are 1″ x 0.6″ / 25mm x 15mm
these are by far the most common size.
Most cards come with a voice and/or data plan. If you want to make phone calls and SMS’s you’ll need a voice plan. If you want to transmit data like fetching a webpage, you’ll need a data plan. At this time the FONA library only supports voice functions, so we don’t have any tutorials about HTTP/TCPIP data management
The most important pins are broken out at the bottom of the board. Not all of these are required, but they are all hella useful
These are in rough order of most important (not in linear order like we usually do)
These pins are all 3-5V input safe and if they are an output, the logic level is whatever Vio is set to.
- Vio – THIS IS THE MOST IMPORTANT PIN! This is the pin that you MUST drive with an external voltage from 3V-5V to set the logic level converter. The converter also buffers the indicator LEDs so NOTHING will appear to work unless this pin is powered! You should set the voltage to whatever voltage your microcontroller uses for logic. A 5V micro (like Arduino) should have it be 5V, a 3V logic micro should set it to 3V.
- Key – This is also a super important pin (but not as important as Vio). This is the power on/off indicator. Its also tied to the button in the top left. Tie this pin to ground for 2 seconds to turn the module on or off. It’s not a level signal so it isn’t like “low is off, high is on” – instead you must pulse it for 2 seconds to turn off/on. The module comes by default off. Tie this permanently to ground if you never want your micro to turn off the FONA for power saving
- PS – this is the Power Status pin. It is low when the module is off and high when the module has power. If you’re using the Key button or pin, you can monitor this pad to see when the module’s booted up. This is tied to the Pwr LED too.
- NS – this is the Network Status pin. It pulses to signal the current status of the module. This is also tied to the Net LED so for more detail see the LEDs section below.
- Reset – this is module hard reset pin. By default it has a high pull-up (module not in reset). If you absolutely got the module in a bad space, toggle this pin low for 100ms to perform a hard reset.
- RX & TX – OK now that I made you read all that you can actually use the UART pins. The module uses UART to send and receive commands and data. These pins are auto-baud so whatever baud rate you send “AT” after reset or boot is the baud rate is used. RX is into the module, TX is out of the module.
- RI – this is the Ring Indicator. It is basically the ‘interrupt’ out pin from the module. It is by default high and will pulse low for 120ms when a call is received. It can also be configured to pulse when an SMS is received.
- SPK+ and – : This is for connecting an external 8 ohm speaker, max 1W. You can configure the module to route calls and FM radio to the headset or the external audio. The two pins are differential so they don’t have output DC blocking capacitors. You cannot connect this to a stereo, powered speakers or other non-differential amplifier without adding a 100uF+ blocking cap in series to the + pin and then not using the – pin. Instead, your amp should use GND for the – reference
- MIC + and –: this is for connecting an external electret microphone, it will bias the mic with 2V. Most electrets will work just fine. No extra circuitry is required for the mic such as a biaser or amplifier, just wire it up directly!
For more detail: Adafruit FONA