clocksimswitches
My setup is as on png above, I am using sim800L gsm module, by trial and error i discovered that i can connect sim pins: (rst,gnd,io and clk) and the module detects and connect to GSM without connecting power to sim vcc pin, i also read that sim vcc is optional.
what i want to do is somehow switch clk signal so that one sim card is detected by module at a time, i can do it with manual switch but how can i do it with electrical switch?. pls help.
What you should ideally link to, as well as the useful top page, is the circuit diagram., as that is what you are inquiring about. It is found here
A lot of the content in your questions would be addressed by readin their FAQ well and/or by looking on web for IM card informatiin.
In their FAQ they say:
"Uses a serial port" and the circuit diagram should give you an immense guide.
Look at the circuit names on the SIM card.
Only on is data related, and that is named "I/O".
DATA IN:
This pin is driven by Q1. When Q1 is on the pin is pulled low.
When Q1 id off the pin is pulled high by R3.
That action allows data to be sent TO the SIM.
DATA OUT And, when Q1 is off, if the SIM toggles the I/O line then R3 will be pulled low by the SIM (Q1 has nio ffect as it is off) and FTDI-RX line and IC1d both "see" this data from the SIM.
So, that covers how data can get to and from the SIM.
The rest is a matter of specifications.
A lot on this will be in the FAQ and more via eg Gargoyle.
Circuit diagram: http://www.ladyada.net/make/simreader/simreaderv1_0.png
What you need is a pull-up resistor.
The Arduino whebsite has a nice tutorial (with software) on using a pushbutton.
We connect three wires to the Arduino board. The first goes from one leg of the pushbutton through a pull-up resistor (here 2.2 KOhms) to the 5 volt supply. The second goes from the corresponding leg of the pushbutton to ground. The third connects to a digital i/o pin (here pin 7) which reads the button's state.
Best Answer
Using analog multiplexer is simple and easy solution.
In the example diagram attached, the two audio source can be two sim cards. SIM-CLK and SIM-DATA can be now shared between two ICs, with the help of one spare GPIO line used to select between two cards.
Remember that it's a bidirectional switch, hence the applications are simply vivid.