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Sending data without wifi

Posted: Sat Oct 05, 2019 3:17 am
by Zilla707
Is there a way to send data from one pi to another pi without using wifi? I am thinking of building a drone with RPi, but I need a way to send data, and maybe images without wifi, and preferably without much lag. Any ideas?

Re: Sending data without wifi

Posted: Sat Oct 05, 2019 6:38 am
by Pi4Bob
Have you seen these?

nRF24 L01 they can transmit farther, especially the ones with external antennas

Re: Sending data without wifi

Posted: Sat Oct 05, 2019 6:50 am
by B.Goode
Zilla707 wrote:
Sat Oct 05, 2019 3:17 am
Is there a way to send data from one pi to another pi without using wifi? I am thinking of building a drone with RPi, but I need a way to send data, and maybe images without wifi, and preferably without much lag. Any ideas?

Cabled Ethernet

Bluetooth

Asynchronous Serial (UART)

SPI/i2c

The above are all 'native' to the RPi hardware.


There are other technologies you could add with 3-party hardware, such as 433mhz radio.



Over what distance do you need to transfer data?

And why not WiFi?

Re: Sending data without wifi

Posted: Sun Oct 06, 2019 6:26 pm
by Zilla707
I want to build a drone, with a RasPi, sense hat, and the RPi camera. So what I want is to be able to send the data (preferably without having to buy, like, cell service or something), without lag, for the FPV. So I would need to send commands to the drone's pi, and receive pics back from it. And with wifi or bluetooth, like the ones you can buy, the range isn't great and if the drone goes to far, the FPV lags out. If there's a way to get a bigger distance, that would be great, but if i'm asking for something dumb, and far-fetched, please tell me so. I don't have much, (if any), experience in this area of computing.

Re: Sending data without wifi

Posted: Sun Oct 06, 2019 6:35 pm
by B.Goode
Zilla707 wrote:
Sun Oct 06, 2019 6:26 pm
I want to build a drone, with a RasPi, sense hat, and the RPi camera. So what I want is to be able to send the data (preferably without having to buy, like, cell service or something), without lag, for the FPV. So I would need to send commands to the drone's pi, and receive pics back from it. And with wifi or bluetooth, like the ones you can buy, the range isn't great and if the drone goes to far, the FPV lags out. If there's a way to get a bigger distance, that would be great, but if i'm asking for something dumb, and far-fetched, please tell me so. I don't have much, (if any), experience in this area of computing.


Suggest you lookout for discussions involving the High Altitude Ballooning community.

https://www.daveakerman.com/

https://www.raspberrypi.org/blog/pytrac ... -software/

Re: Sending data without wifi

Posted: Sun Oct 06, 2019 9:15 pm
by Zilla707
Thanks, I'll check it out.

Re: Sending data without wifi

Posted: Mon Oct 07, 2019 10:20 pm
by Zilla707
Does anyone happen to know if there's much, or any lag in between sending, and receiving data, if the range isn't too big? (like 1 mile)

Re: Sending data without wifi

Posted: Wed Oct 09, 2019 1:57 pm
by Andyroo
Zilla707 wrote:
Mon Oct 07, 2019 10:20 pm
Does anyone happen to know if there's much, or any lag in between sending, and receiving data, if the range isn't too big? (like 1 mile)
Virtually none as radio waves travel at the speed of light (186,000 miles per second give or take a furlong or two per fortnight to allow for atmosphere compared to vacuum).

Re: Sending data without wifi

Posted: Wed Oct 09, 2019 5:44 pm
by drgeoff
If you want reasonable resolution video and low latency you need Mbit/s. That rules out Bluetooth, Asynchronous Serial (UART), SPI/i2c, 433Mhz radio.

Re: Sending data without wifi

Posted: Wed Oct 09, 2019 8:23 pm
by wolf.z
Well, transmitting from drones, you are stuck with ISM band radio and or SRD radio. Any attempt for gaining less latency will cause you to become a radio amateur (without further discussion). That said

there is an ongoing project using WIFI hardware in injection mode, targetting image broadcast. That is, minimizing latency of the radio level transmission by avoiding networking, just using radio part of WIFI hardware. Anyway, transmitting moving images involves image compression, causing a latency of about 8 frames or so. Start with EZ-wifibroadcast since Rodizio provides an image that works out of the box. It is an all digital FPV solution from the drone amateur's community. Range out of the box should be about hundreds of meters.
https://github.com/rodizio1/ez-wifibroadcast/wiki

Re: Sending data without wifi

Posted: Thu Oct 10, 2019 2:21 am
by Zilla707
That looks good. I'll check it out, and thanks for all of the good ideas.