Using XBee S1 to send GPS through a DIO pin

Wireless & IoT
1

Hey SparkFunners!

I have two XBees and a Venus GPS that outputs regular NMEA sentences. I have the Tx of the GPS hooked up into the D0 pin. The transmitter has ATD0 set to 3. The receiver has ATD1 set to 4. Is it possible to get the data out in this configuration? I’d rather not use the UART on the transmitter XBee, because I’m using that for something else.

If this isn’t doable this way, how would I have two different serial devices on one XBee?

Thanks in advance guys!

Pranav

2

It is not likely possible. XBee’s are designed for slow data collecting and the Data pins are only sampled the states transmitted at a slow periodic rate or when queried remotely.

It would be best to connect the GPS serial output to the XBee serial input at the same Baud rate.

If this isn’t doable this way, how would I have two different serial devices on one XBee?

You can't directly.

One solution is to use a processor (PIC, Ardiuno, etc) that inputs the two serial sources then arbitrate them into one serial output.

3

Thanks for responding!

I’m trying to keep this light and small. Which of those do you suggest? I could go for something like an arduino nano pro or for a PIC. I think I have a few PICAXEs somewhere. The other requirement is that they be able to pass lots of data through. I actually have an HD USB webcam streaming through the UART.

Of those above or perhaps another not listed, which do you recommend?

Thanks again in advance.

Pranav

4

It will depend on the total amount of data that needs to flow. How many bits per second do you need total?

An XBee can only pass about 57.6kBaud continuously.

5

I actually hope to upgrade to the XTend 900. The supposedly 40 mile line of sight one. That one can do up to 115kBaud. Would that be enough? Is there any way that I can see how much data would be sent out the webcam on full HD?

Thanks for your time.

Pranav

6

Is there any way that I can see how much data would be sent out the webcam on full HD?

Number of pixels ( x 3 if rgb) x number of bits per pixel x number of frames per second = number of bits per second. Fill in the numbers and multiply.

7

Sorry for the delay.

So in short, if I did the math properly:

1080x1920px/image3colors/px1byte/color*8bits/byte=49766400bits/image

This means that per image, I’ll need:

49766400bits/image*1second/115200bits=432 seconds/image

Wow. That’s not going to happen. Are there other forms of long range wireless communication that has a much higher baud rate? Somewhere in the MBaud? Or has that not been released yet?

Thanks.

8

Yep, that is a issue with video.

With an XBee its even worse since an XBee can’t really do 115.2kBaud with a continuous data stream.

There are longer range RF device that have the data rate you wish but they are not cheap.

If the range is fairly short (~100m) then you might be able to use 802.11 (WiFi).

Another solution is to use a camera with a much lower resolution and maybe even B&W to keep the cost down.