gsmintegrated-circuitsim
i have a GSM breakout board and a 4g dongle. I'm curious whether it is possible to share one SIM card between both of them? Does anyone know if there is any IC available to do this?
edit: Only one device would use the sim at a time. Ex. first the gsm module for 30 min then the 4g for 1 hour.
No, they don't have multiple GSM modules. That would drive up cost, size, weight. Since the user is only on one call or the other, there isn't a need for more than on GSM module.
EDIT Jan 31 '12. Wikipedia says there are phones that can use both at once. But I still believe there is only on GSM module.
(1) below added
(1) MAX1840 / 1841
You can probably find a fairly complete answer to your requirement and a hardware solution for the actual card interface in the MAX1840/1841 and associated data sheet and basic application note . While these ICs are sold principally as level translators and support and protection circuitry to interface with SIM cards, the data sheet contains a wealth of information on timings and levels.
They say
The MAX1840/MAX1841 subscriber identity module (SIM)/smart card level translators provide level shifting and electrostatic discharge (ESD) protection for SIM and smart card ports.
These devices integrate two unidirectional level shifters for the reset and clock signals, a bidirectional level shifter for the serial data stream, and ±10kV ESD protection on all card contacts.
The MAX1840 includes a SHDN control input to aid insertion and removal of SIM and smart cards, while the MAX1841 includes a system-side data driver to support system controllers without open-drain outputs.
The logic supply voltage range is +1.4V to +5.5V for the “controller side” and +1.7V to +5.5V for the “card side.” Total supply current is 1.0µA.
Both devices automatically shut down when either power supply is removed. For a comp l e t e S I M c a r d i n t e r f a c e , c o m b i n e t h e M A X 1 8 4 0 / MA X 1 8 4 1 wi t h t h e MA X 1 6 8 6H 0 V / 3 V / 5 V r e g u l a t e d charge pump. The MAX1840/MAX1841 are available in ultra-small 10-pin µMAX packages that are only 1.09mm high and half the area of an 8-pin SO.
The MAX1840/MAX1841 are compliant with GSM test specifications 11.11 and 11.12.
Timing information from datasheet:
20 ns/division
1 uS/division.
(2) A SIM card uses a relatively simple hardware interface
The circuit below from "Lady ADA" is from here. I trimmed it only to make it larger when veiwed here. I would expect pin 7 to be speed sensitive as shown here due to RC time constant and pin 2 may be. The rest of the circuit is "somewhat kluged" but shows what is involved. You would want to provide buffering at both ends. but this circuit plus the associated code shows what is required.
The whole SIM reader project can be found here
Eagle schematic and PCB layout provided.
Their product (from the above website):
.
Best Answer
It's not possible to share one SIM between two devices.
Well, not easily, anyway. The SIM contains a microcontroller and there is quite a complex communication protocol between it and the device it's installed in that would be confused by connecting two devices to the same SIM. That's in addition to the fact that the two devices would often be trying to drive the same SIM input pins to opposing states at the same time.
You would need to implement an intelligent device that would provide two SIM interfaces, one to each device, and a third interface to the SIM itself, and maintain a separate channel of communication for each interface.
Some service providers allow two SIMs to share the same plan, which is about as close as you're going to get without a great deal of work.