AaronInSpace 4 Posted September 21, 2011 Share Posted September 21, 2011 Hey all, Working up a new project where I want to drive my RC car using an onboard camera module transmitting over some radio frequency to me. It is also similar to something I want to do at work in that I want to transmit video or images with limited bandwidth. Also it will eventually lead to doing a FPV RC airplane (check these out on youtube if you don't know what they are...theyre awesome) which will require longer distances and higher framerates and quality. My main question is this: is there a format of image which can easily be sent over radio. The limitations are that if you use JPEG, if one bit gets flipped, you can corrupt the whole file and get nothing. So is there something that is more susceptible to loss? Also is there an image format that can be built up pixel by pixel on the receiving end and displayed as each pixel comes in? I saw a guy do a high-altitude balloon on Hackaday using some sort of image format that he split up into hundreds or thousands of packets that each could be reassembled as the packets came in using some programming on the groundstation. Feel free to yak it up. I'm listening to any sort of advice and comments. Quote Link to post Share on other sites
bluehash 1,581 Posted September 21, 2011 Share Posted September 21, 2011 if you want real time video, the analog way is the best. Once you digitize it, you wil need to take bandwidth into consideration. You do get serial jpeg cameras which you can hook onto a zigbee and get wireless vide, but that will limit your framerate to maybe 3-4 images/second. http://www.sparkfun.com/products/9334 AaronInSpace 1 Quote Link to post Share on other sites
thanhtran 10 Posted September 22, 2011 Share Posted September 22, 2011 I've not heard of any RC plane / RC heli guys doing any FPV by packet video yet (except the AR Drone, but its video is pretty jerky from what I've seen). From what I've seen, they all use analog video transmitter for FPV. They even complained about the latency of the GoPro HD camera with its video out mode transmitted via analog transmitter being not fast enough. I didn't see any problem with this camera though. AaronInSpace 1 Quote Link to post Share on other sites
AaronInSpace 4 Posted September 23, 2011 Author Share Posted September 23, 2011 Thanks all. I will look into analog video but I am still thinking of doing it digitally. You don't learn much buying a kit and plugging it into your uC. For me this is all about learning (oh ya and playing!). The one at work is to test a radio system anyways and so changing the way it transmits is not a possibility. I can only change the data I am sending. So what format could you use that wouldn't be screwed if you lost a packet the way that a JPEG is? Quote Link to post Share on other sites
bluehash 1,581 Posted September 24, 2011 Share Posted September 24, 2011 Well, if you use zigbee's, error correction is built in and independent of the packet(provided a packet is within the error correction range). I haven't tried it. Just something I read about digi's zigbees. AaronInSpace 1 Quote Link to post Share on other sites
HylianSavior 37 Posted September 25, 2011 Share Posted September 25, 2011 I roughly calculated the bandwidth for live digital video over the 2.4 GHz band for my quadrotor a while ago. You get 250 kilobits per second, assuming no lost packets. Let's say a reasonably sized (smaller than VGA) compressed still image runs around 16 kilobytes, which equals 128 kilobits. You'd basically get ~2 fps on compressed data, assuming no error correction on lost packets. If you end up using something like a router with dd-wrt as a control board, you might get some better bandwidth with wifi, but wifi tends to be bad when things are moving about and causing interference. In short, if you want live video, analog is the (only) way to go, especially if you want an FPV plane. If you want the occasional still frame, digital might still work. I haven't seen any digital FPV systems on RC planes, though. AaronInSpace 1 Quote Link to post Share on other sites
AaronInSpace 4 Posted September 26, 2011 Author Share Posted September 26, 2011 Okay so perhaps that idea is out. I appreciate all the feedback! If anyone comes up with some idea or product we haven't thought of, let me know! Quote Link to post Share on other sites
AaronInSpace 4 Posted September 30, 2011 Author Share Posted September 30, 2011 Why not use WiFi for the car? WiFi can stream video easily. Problem will be finding one with a serial interface fast enough. Quote Link to post Share on other sites
gordon 229 Posted September 30, 2011 Share Posted September 30, 2011 How about http://littlebirdelectronics.com/produc ... 802-11-b-g (if you ignore the Arduino sticker, seems like a fit, a bit on the expensive side, though)? Quote Link to post Share on other sites
AaronInSpace 4 Posted September 30, 2011 Author Share Posted September 30, 2011 Thanks for the find! Pretty good baud rate but still a bit slow: "Baud Rate : Max 921,600bps" I'm now looking at ones that have SPI. Anyone got an idea of how fast a SPI can run? I see the G2553 spec sheet says frequency is system frequency...So if i clock my 2553 to 16 MHz, what bps is that? It's not quite so easy for me to figure out as UARTs... I'm specifically looking at the Wifi Xbee but I can't figure out the models offered...very confusing: http://www.digi.com/products/wireless-w ... i#overview Also looking at the TiWi-R2 offered by LS Research (http://www.lsr.com/products/radio_modul ... wi-r2.aspx) which I saw someone else working with on here. It says it has "SDIO" which I don't think the MSP430 has the capability for, and the UART speeds (up to 4000 kbps ) is something I wouldn't know how to reach. Lastly, I found this guy: RFM's WSN802GC (http://www.rfm.com/products/spec_sheet. ... d=WSN802GC) which has SPI and seems like it could kick butt, but its pricier. Quote Link to post Share on other sites
AaronInSpace 4 Posted October 6, 2011 Author Share Posted October 6, 2011 Just an update: I went with the XBee WiFi module and a breakout board from SparkFun. Now I just need a camera module capable of 900x500 or so resolution, capable of transmitting 15 fps or so. Since I plan to use a Launchpad, high frequency crystals are out so therefore high speed UART is out. Will have to be an SPI camera. Those seem few and far apart and all high-priced so far. Can anyone think of any other possibilities for a camera? Quote Link to post Share on other sites
HylianSavior 37 Posted October 7, 2011 Share Posted October 7, 2011 I also looked into cameras for my quadrotor. Here's what I came up with: http://www.micro4you.com/store/modules/ ... -fifo.html http://www.emartee.com/product/41804/OV ... a%20Module There are other very similar cameras, but this one has a FIFO and a nice black PCB to block out light. Although I'm questioning whether the MSP430 can push frames fast enough for video... My initial guess would be no. As for trying out wifi, please do return with results. I still wouldn't recommend it on anything flying, but it'll probably be fine on an RC car that doesn't go too far away. Note that wifi tends to suck up a lot of power in return for that transmission speed. AaronInSpace 1 Quote Link to post Share on other sites
AaronInSpace 4 Posted November 17, 2011 Author Share Posted November 17, 2011 Update: this thing is stuck up with the WiFi module not working. Still working on getting simple UART to work to the device. No response from it from either my FTDI or straight through the LaunchPad's USB. Quote Link to post Share on other sites
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