[SOLVED] [moved] How to choose GPS module for GPS CLOCK ?

[jay1691]

Hello All,

I need a help for my upcoming project that is GPS CLOCK. I want basic selection guide for choosing GPS module for CLOCK. As i surf i got basic selection idea for GPS position detection. Is there anything different for GPS CLOCK ???

 

[shaiko]

Re: How to choose GPS module for GPS CLOCK ?

What is the question exactly?
Every modern GPS module I know of has a PPS output.

 

[Aussie Susan]

It also depends on how accurate the GPS clock has to be.
For example, is the PPS output sufficient for what you want? While the pulse itself may be accurately timed (to microseconds), can you afford to wait for the next 'second' to get a pulse?
Also many GPS chips output NMEA strings that contain the time: can you afford the time delay between the GPS chip determining the signals from the satellites, generating the string, sending it at whatever baud rate, you decoding it and the setting your clock - all that could take several mSec!
I think you need to examine what you are trying to actually achieve from your GPS clock and base your design decisions on that.
Susan

 

[jay1691]

Hello Everyone,

I have selected Quectel L80 GPS Module for my project. It gives 1HZ 1PPS out signal.
Now i want to choose MCU for that application. In that i want 1 UART , 5 GPIOs .
My question is how can i take care of 1HZ speed can be decoded by MCU ?
Please suggest me any chipper MCU for that.

 

[Aussie Susan]

It all depends on what you want to do with the 1Hz signal.
If you are simply using it to create your own RTC then the next question is how accurate does it have to be? In other words, what latency can you afford between the rising edge (if that it the one you should use) and the actual update of the second's unit digit. (Apple claim that all of the Apple Watch second-hands move at exactly the same time all around the world, but they go to a lot of trouble to synchronise then. Therefore the question for you is do you need to go to that level or is something that is +/- 0.5 or 0.1 or 0.001 second OK?)
Also questions such as the supply voltage, maximum current draw (and possibly the related question of battery life), chip size, mounting requirements (DIP, surface mount, ball or pin...), do you need a crystal or is an internal (normally RC-based) oscillator sufficient and lots more all come into the device selection.
The requirement for 1 UART, 5GPIOs and (presumably) an I/O for the 1Hz signal should not be hard to meet once you have an idea about the other criteria.
Susan