Re: [Paparazzi-devel] How to Synchronizing the two Tiny boards?

[Zhang Qiuchen]

Hi Martin,

Thank you for the prompt reply. 
In order to synchronize all my data, I'm thinking if it's possible to first 
synchronize the two processors and then add time stamp to the telemetry data 
before it is sent to the ground station; or add time stamp to the data gathered 
from the Tiny board before store it in the SD card?
Or do you have any other suggestion for this synchronization?

Thanks a lot !
Autumn  
________________________________________
From: address@hidden address@hidden on behalf of Martin Mueller address@hidden
Sent: Friday, October 26, 2012 5:30 PM
To: address@hidden
Subject: Re: [Paparazzi-devel] How to Synchronizing the two Tiny boards?

Hi Autumn,

> My name is Autumn and I'm working on a system that uses paparazzi on a Tiny
> v2.11 board (with LPC2148 as the main processor). I added a TWOG in addition
> to the main autopilot Tiny to take data from some sensor and log them to a SD
> card. However, the data that is logged in the SD card and the data sent back
> via telemetry has non-matching time stamps. I wonder if I can synchronize the
> two processors by configure the TWOG to use external clock and physically
> connect the clock pin from Tiny to the TWOG.

the on-board TWOG log data is synchronized to the TWOGs 12MHz Quarz and starts
when the TWOG is booted. The timestamp is added to each messsage by the TWOG as
it is written to SD card.

The log file that is recorded in the ground station is started when the ground
software is executed. The timestamp is generated in the laptop as the message is
received. There will be some jitter caused by the radio link (retries, random tx
delay).

> Have anybody ever met problems on asynchronized data from two processors or
> between telemetry data and data stored on board?

The Tiny does not generate any timestamp in your setup. It is the TWOG and the
laptop.

Martin

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