Sim300 voltage levels

[MScofield]

sim300 pic

Hi All,

I'm interfacing the Sim300 with a PIC Microcontroller. The PIC works with 3,3V High Output Level and the Sim300 works with 2,051V to 3,23V as High Input voltage.

Acording to the Sim300 Datasheet:
(Logic high input Min: 0.7 *VDD_EXT = 2,051V)
(Logic high input Max: VDD_EXT +0.3V = 3,23V)

Which is the best way to balance the PIC output level with the Sim300 Input Level?

At the moment i'm using a 2.4V Zener Diode direct in the PIC pin, but one can use a transistor driver.

How do you make this is your project?

 

[GSM Man]

pic+sim300

The digital inputs of the SIM300 can handle up to 3.3V. As long as you are running your PIC at less the 3.3V you can connect the pins directly.

 

[MScofield]

max voltage levels

Thanks, it's better for me...but why the datasheet specifies thar the max and min Logic levels of serial ports pins? 3.3V is above the input max high level.

I've just connected the pins directly, when I put the PIC pin to high, it reaches only 700mV.

 

[GSM Man]

linux driver for sim300

I don't know what datasheet you're looking at, but all of the datasheets I have indicate that "VIHmax = 2.93V+0.3" which is 3.23V. Also, they state that the absolute maximum voltage on any digital pin is 3.3V.

 

[MScofield]

sim300 vdd_ext

Exact, this means that the any digital pin tolerate 3.3V without damage it, but the maximal voltage that it understand as "High Level" is 3.23, which is 0.07V less than 3.3V High Level output of the PIC.