I know the EM406 require 4.5-6.5V input. Just wondering if the RX and TX pins are 5V tolerant. It appears so based on the RS232-Eval board. Just wanted to clarify though.
The EM406 has on board voltage regulation, which is why the input voltage can be as high as 6.5V. The actual logic is 3.3V, so I would be concerned hooking it up to 5volts.
Owen
I need to hook the GPS module up to a data logger which uses 5v TTL logic.
This GPS module uses 2.8v CMOS level logic. I am not sure what the max min voltage levels are for standard TTL to register the high and low states so the question is will hooking up the GPS module to a TTL level input work or not.
If no, what sort of a chip or circuit do I need to shift the logic level from 2.8v to 5v?
Sorry for the beginner question.
Thanks,
Serge
All I have been using the sparkfun evkit to check on this problem and have not had a problem receiving data to a 5V PIC. I have not had to send data to the EM406 unit and have not tested whether sending 5V to to this part. Since I am using the EM406 in its default configuration I am not to worried about this.
ssozonoff:
I need to hook the GPS module up to a data logger which uses 5v TTL logic.This GPS module uses 2.8v CMOS level logic. I am not sure what the max min voltage levels are for standard TTL to register the high and low states so the question is will hooking up the GPS module to a TTL level input work or not.
If no, what sort of a chip or circuit do I need to shift the logic level from 2.8v to 5v?
Sorry for the beginner question.
Thanks,
Serge
I’m not positive on this, but I believe all PICs are tolerant of 2.8v CMOS logic INPUT. I am positive that the 18F452 is. It’s best to chek the datasheet on both the GPS and the logger’s microcontroller to see what the maximum voltage for a low output/input is, and what the minimum voltage for a high output/input is. However, I’m pretty sure that it’s CMOS logic that’s quite succeptible to latch-up problems, and wouldn’t be tolerant to any input beyond it’s maximum rating - usually something like 3.3V.
The easiest way to translate logic between two voltage levels is to use a non-inverting hex buffer, feed its input with the higher voltage output, power it at the lower voltage’s typical maximum, and feed its output into the lower logic level’s input. In most cases, you should be able to get away with feeding the output from the 2.8v CMOS directly into the 5v input, but I’m pretty sure that only works if the inputs are high-impedance inputs.
Take a look at the schematic for documentation on my sd gps data logger. In the lower right hand corner of the schematic is the logic level translation I had to implement to ensure a reliable serial connection. it uses 2 resistors and a NPN 2n2222A
Wait… so the EM406 uses 3.3V or 2.8V as logic high??
this thread is confusing…
I’m trying to interface the chip with an AVR atmega128
ohararp:
Take a look at the schematic for documentation on my sd gps data logger. In the lower right hand corner of the schematic is the logic level translation I had to implement to ensure a reliable serial connection. it uses 2 resistors and a NPN 2n2222A
so basically you’re using a transistor to leel shift?
Yes this is simply a logic shifting scheme. I am told (not tested) it should be good to about 19200 baud.
I don’t see how it works…
for level shifting… is it possible to use an op amp set up as a comparator?
ohararp: whats the max speed you can get using the 2N2222A based level shifter?
Any idea if those will work all the way at 115kbaud?
I have only needed the 4800 baud rate. Since the schematic was recommended from someone else they thought the method should be good to 38400 baud.
i want connect EM-406 to pc with com port
but i dont know do it
please guid me
You will need to use a scheme similar to this: