Sending camera images using CC1101

[vidyagopan27]

Me and my project partner are currently designing a RX/TX system for a high altitude balloon launch . This is for the Adler Planetarium .We have finalized to use a CC1101 TI Transceiver system . Our requirement for the time being is to transfer camera images from a RS232 camera wirelessly to CC1101 in the lab . are there any special interfacing required for this ? COuld anyone suggest a suitable RS232 camera ?

 

[E Kafeman]

Why not use I2C? You can then use most cellphone cameras and simpler interfacing against modern MCU's.
**broken link removed**

 

[vidyagopan27]

Thanks a lot !But i dont think CC1101 supports I2C ? Not sure . I am jsut going through the manual . will I ahve to use another module that will attach to the CC1101 for this ? I hope I am not asking a dumb question. Is there any option I can connect it directly ?

 

[E Kafeman]

CC1101 doesn't support RS232 either. You need to have a MCU that can handle SPI to do anything useful with CC1101.

 

[vidyagopan27]

I have an SPI interface ? How can I interface that with the CC1101 ?
I have the CC1101 module u see . here is the link for that :

**broken link removed**

I hope this module works . because this is the exact requirement for my project . I even calculated the link budget for the same .

 

[E Kafeman]

Yes you have a CC1101 with SPI interface. I guess you have programmed it by sending commands from a PC via a RS232toSPI converter to make it start communicating with another CC1101 module that also have a computer instead of a MCU as controller.
Then you connect the camera, how do CC1101 know what register inside CC1101 that picture data not should control? It have ~ 100 registers for different settings. Have you planned to send the PC in the air as controller?
Have you calculated time to transfer one picture over RS232?

 

[vidyagopan27]

No we cant send the PC in air as a controller .There is an MCU called the Basic stamp which can be send as a controller but if we send that as a controller how to we connect the camera . there is only one SPI itnerface right . wither it can be camera or ti can be controller . Another way is to send commands to the CC1101 using the CC1101 on the ground ? right now the camera set to take pictures every 5 secs ? For testing purposes we are thinking of testing it from a the top of a very high building ?

---------- Post added at 20:47 ---------- Previous post was at 20:45 ----------

Another question is that will the CC1101 convert the images to the way it ahs to be transmitted ? I know it has a modulator demodulator of its own ?

 

[E Kafeman]

If it is a low cost project, use USB. Cheap web camera and cheap sensors such as GPS and no do not transfer all data to ground, store it in a cheap USB memory.
SPI can support many modules but the thing is that SPI is a protocol, a data streams that must be built according to a certain structure. That is handled by software in your computer when it is sending data to the RS232toSPI interface. A camera does not know anything about how SPI signals must be addressed and such so it is not a good idea to connect a RS232 camera directly to a SPI-bus. The camera is better connected to a MCU as also the camera must have intelligent instructions what picture format, video or still pictures...
In a computer do we call it for drivers, these files that contains information about how to communicate with mouse, keyboard, camera, USB headset or USB harddrive. You still need this kind of drivers to be able to handle a camera a GPS-radio or a CC1101-radio so that is why a MCU is used.

No CC1101 will not convert the images, it doesn't care about what kind of data it is. It is your job to find best software/hardware solution to convert actual picture format to a correct SPI format or else will nothing at all be transferred. This conversion is what a PC normally do when a web camera is connected. It convert that information in a numerous format for storing, printing or sending it to screen. Even in a simple RS232toUSB converter it must be intelligence in form of a MCU to convert between these formats. Try to feed a USB with wrong protocol and nothing will happen.

If you send control-information from ground to CC1101, how do it now that it is control information intended for it self?

Just an quick estimation that could be wrong, but RS232 - assume 19.6 kbit/s, not sure that more is recommended over CC1101 anyway. It is about 2 kB picture per second . A 2 MB picture will then take 1000 seconds to transfer. 1000/60 = 17 minutes.
You said you have done link budget and I assume you started at camera interface to find out needed bandwidth and ended in some storage interface at ground. I guess you then need to compress picture to reduce transfer time or you maybe have another solution if you plan to take a picture each 5th second?

 

[vidyagopan27]

So I have decided to connect an RS232 to camera to a Basic Stamp II module. Is there any way this can be connected to an SPI interface ?

 

[E Kafeman]

It should not be any problem, you need to program two pins from the stamp for SPI clock and SPI data.

 

[vidyagopan27]

Hi ! Is the Basic Stamp !! better or the Arduino ? What is i use Arduino or the PIC32

 

[E Kafeman]

I had selected the MCU family for which I had best knowledge. Each MCU have different advantages.
As I know 80C51 family best had I probably selected a 80C51F380 for a typical high altitude project were maybe ten simple sensors are read and a few also controlled or activated and such(GPS, temperature, pressure, tracking transmitter, electrical fuse for balloon..) and plenty of flash memory. Maybe also an controllable electrical heater to handle ice and moisture at camera lens. I had used several cameras, if possible from old cellphones both for video and high resolution still pictures in several directions. They are compact and have low weight which is important. Had not used any equipment that had required RS232 as that is a old protocol mainly for communicating via cable over several meters and that is not the need.
80C51F380 have two I2C, one SPI and one USB2.0. Perfect as controller and with USB can all data be saved in a cheap USB memory which have plenty of room for video and big pictures.
It does also have a ADC for reading analog data and internal temp sensor. In total 40 digtal I/O which is useable for power control for all different equipment including need for electrical heating. Else would the electrical source become unnecessary heavy, which limits max achievable height.
80C51 is also simple to program both in C and in assembler and a lot of free software exist such as compilators, debuggers and emulators and a lot of software examples.
It is a relative powerfull processor but it can also consume a lot of power which must be accounted for in total power budget. Some of this heat can of course be reused for heating camera lenses.
If you prefer another MCU family, is up to you and how your needs looks like.
I had also not selected to not download pictures. Costs increased TX bandwidth which reduces receiver sensitivity. Can be compensated by increased TX level or better antennas but that result in increased weight of antennas and battery.
Not storing all data local would be less clever if down-link fails. Using CC1101 requires also probably two antennas if you plan to reach any higher height, one very directive antenna that is pointing downward but also one antenna that can send omnidirectional tracking info because during landing will the directive antenna be pointing at a place maybe 100 miles away.
An alternative, if you is reusing an old cell phone for this project is to let the phone send a SMS with latest known GPS location.
If you still want to only send information via a radio-link, each picture will probably fail more or less as these balloons tend to rotate. Due to this rotation will the antenna be cross polarized compared to ground antenna and you will drop connection during short moments, twice for each turn the transmitter rotates.
This problem is worse compared to a ground2ground connection due to less reflections. Can be compensated by using two receivers. If you also is sending control/information to the balloon, use a protocol that can handle that some parts of information must be resent in case of temporary dropouts.

 

[FvM]

I didn't hear any thoughts about intended range. You won't get far with a 10 mW transmitter, I think.

 

[E Kafeman]

Narrow band between two CC1101, LOS , omnidirectional dipole, you can reach few hundred meters which not is so bad. High altitudes, is a bit unspecified. If intention is to reach 40 km heights, is a pretty good antenna needed.