Discussion in "General help Guidance and Discussion" started by    Mamat    Nov 4, 2010.
Sat Nov 27 2010, 05:36 am
#11
Whether you need a 232 converter depends on what you are connecting to.

A PC serial port puts out high +/- voltages,
so you need a MAX232 to connect to a PC.

A PIC powered from a 5 volt supply will transmit at 5 volts,
this is too much for your module,
so you need to drop the voltage from the PIC to your module by about 2 volts.

This can be done with a simple circuit using 2 resistors as a voltage divider.
The PIC can work with the XBEE output directly.

If the PIC is powered from 3.3 volts, you can connect TX and RX directly.
Sat Nov 27 2010, 04:49 pm
#12
for regulator suggestion you can use LP2981 3.3V LDO to power your PIC.
Mon Nov 29 2010, 08:17 am
#13
from picture,this diagram to setting xbee via pc serial port.i want to know.can i change serial port connection to pic connection?mean pin 14 and13 max232 to pin pic.xbee will work properly or not?
Mon Nov 29 2010, 11:21 am
#14
hi Mamat
drive max 232 on 3.3 volt
it should also work on 3.3 v
so max and xbee module voltage level becomes equal
secondly do not connect the xbee and controller tx, rx pins to max 232 at the same point
that may cause data collision
max 232 with xbee should be separate if u want to use xbee with controller then now it should remove from max 232 side
now it should only connected to controller
in one time it should connected with one thing pc or controller
Tue Nov 30 2010, 03:08 pm
#15
max232 does not work on 3.3 so its better to use MAX3232 its a 3.3V IC. if your end device is 3.3V please never use MAX232.

check datasheet of MAX3232.
Mon Jan 17 2011, 08:49 pm
#16
Ajay say "max232 does not work on 3.3 so its better to use MAX3232 its a 3.3V IC. if your end device is 3.3V please never use MAX232".
My question is my xbee module run 3.3volt and pic 5volt.Can i connect pic to max3232 to xbee?
Mon Jan 17 2011, 11:06 pm
#17
which PIC are you using? usually PIC microcontroller have wide operating range. so probably your pic can work on 3.3V

moreover XBEE does not need a line driver as its communication port works on TTL levels. if you really need something then its a level converter which converts 5V to 3.3 and 3.3 to 5V. The simplest method of making a level converter is to use a transistor circuit. There is no need of converting 3.3 to 5V as PIC can understand 3.3V as high.
Tue Jan 18 2011, 07:19 am
#18
ajay after i check my pic datasheet PIC18F4620.wide range supply voltage is 2-5 volt.So this mean i can supply 3.3volt on my pic and xbee and then i can connect directly between this two device.This right or not ajay?
And i not understand what are you talking about TTL and line driver,i hope i no need this after i apply 3.3volt on pic.
Tue Jan 18 2011, 11:39 pm
#19
@ Mamat

ajay after i check my pic datasheet PIC18F4620.wide range supply voltage is 2-5 volt.So this mean i can supply 3.3volt on my pic and xbee and then i can connect directly between this two device.This right or not ajay?


yes it is ok u can use it

And i not understand what are you talking about TTL and line driver,i hope i no need this after i apply 3.3volt on pic.


TTL is a transistor transistor logic
its logic level for 0 is 0 to 0.8 and for 1 2.5 to 5 volt
@ ajay
can u explain one thing that i often confuse me
74ls series is a TTL that operating voltage is only 5.5 volt maximum.
cd 40xx series is CMOS as it has 15 volt maximum
now computer logic is +3 to +25 as 0 and -3 to -25 as 1
at89c51 is cmos as c stand for cmos and it operate on 5.5 volt maximum as 74LS xx series and even cd40xx is a cmos and operate at 15 volt maximum
can anyone explain me what these differences are in TTL,CMOS and PC logic levels.

Wed Jan 19 2011, 08:13 am
#20
my pic wide range 2-5volt,when i try output at led very low and not enough power supply.now i decide to use 5volt for pic and connect to max3232 and connect to xbee.Can or not?

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