Multiple Sim card to a single sim300

[sudarshann]

Hi Friends,
I have the following doubts regarding interfacing multiple sim cards with a single sim300 module.

As you know sim card has the following pins

1 Vcc
2 Reset
3 CLK
4 Gnd
5 Vpp (not used)
6 I/O



In my case I need to use 32 sim cards with a single SIM300. Meaning only one sim out of 32 will be active. and active sim is decided by the mcu controlling the system.

The doubt i have is how can connect all the sim cards to same sim300. Can I do the below methods
1) tie vcc, reset, gnd, IO together and connect the clock signal of the required sim to the sim 300
2) I need a active sim indicator. to which line can i connect an led (smd) for indication.


Please provide me a solution for this issue.

Thanks in advance

 

[FvM]

Without CLK connected the card might stay in an undefined state, I won't be sure that I/O isn't possibly driving out. Also the capacitive load might require to disconnect I/O.

I may be that the mobile devices switches off VCC while no accessing the card, otherwise you would monitor clock activity.

 

[sudarshann]

Dear Sir,
You mean to say that I can tie up gnd, reset, clk, io together and switch Vcc alone. is that what you mean ?
Will that work?

or I need to use some package like the below
https://www.fairchildsemi.com/pf/FS/FSA2567.html
https://www.onsemi.com/PowerSolutions/product.do?id=NLAS3899

If i use a dual sim switcher cascading will they work ?
like below

sim 1
=> 12
sim 2
=> 1234
sim 3
=> 34
sim 4
........
....
......

.....
=> ....
sim 31
=> 3132
sim 32

 

[FvM]

You mean to say that I can tie up gnd, reset, clk, io together and switch Vcc alone. is that what you mean ?
Will that work?

No. I said that at least I/O should be switched besides CLK. Switching all four connected non-ground card contacts would be the safe variant.

Besides a 5-level binary tree of DT (double throw) switches, I would consider other multiplexers.

 

[sudarshann]

Dear Sir,
I have tired muxing 4 lines of 4 sim card as binary tree. but the design is getting much complex than I expected.
you mentioned other multiplexers what are the other options that you suggest Sir.

the devices like below
https://www.addpac.com/addpac_eng2/customer_notice_view.php?notice_id=306

they have gone more than 512 sim cards equipment. and 16 sims per module in it.

Can you suggest to get atleast to 8 sim per SIM900 module ?

Thank you