Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: ordertaker on November 28, 2009, 09:34:07 PM

Title: confused about blackfin-axon
Post by: ordertaker on November 28, 2009, 09:34:07 PM

hello, I am a noob and i'm a bit confused with the combination of the blackfin camera and axon.. why do we need to incorporate the axon with the blackfin camera? is blackfin's capability limited?

we are currently working on a project which concerns the blackfin camera, it is like the ERP but for surveillance only. It is controlled via wi-fi, has a pan/tilt just like ERP which we aim to control by the output of an accelerometer attached to a vision goggles also via wi-fi (refer to the video):
robot controlled by head mounted display (http://www.youtube.com/watch?v=sCj4uWkOWHI#noexternalembed)

is it possible without the use of axon?

Title: Re: confused about blackfin-axon
Post by: SmAsH on November 28, 2009, 11:01:54 PM

Yes, they are two completely separate things. The package was just to make it cheaper for people who wanted both.

Title: Re: confused about blackfin-axon
Post by: Admin on November 29, 2009, 08:33:56 PM

The Blackfin can handle the servos, and it has two UART ports . . . but you may not find coding it to be as easy, and you'd need to wire up a separate power bus to attach servos.

As for the accelerometer, I'm not sure if the Blackfin has ADC. The datasheet isn't so clear . . . you'll have to read up on that.

I'm biased, yes, but my vote says using the Axon (or any other additional multi-UART microcontroller) will make it much easier to make a full robot out of the Blackfin. The advantage with the Axon is that the code is already done for you, easy to hack, and just plug and play. Is this for a one-off robot, or a product?

Try asking Surveyor what they think will be easiest/best for your app, too. I'm definitely no Blackfin expert!

Title: Re: confused about blackfin-axon
Post by: Joker94 on November 30, 2009, 04:24:24 AM

I think get the pakage as if you want to make another robot later without the Blackfin on board you have an axon. And as admin said codeing will be alot easier as alot is already dine for you.

Title: Re: confused about blackfin-axon
Post by: hgordon on November 30, 2009, 10:19:59 AM

Blackfin doesn't have A/D and has only 4 servo / pwm channels, so without the Axon, you might otherwise have to add i/o via I2C interface.  The main advantage of the Blackfin is 500MHz dual ALU processing with 32MB memory and direct camera interface  - this is 20x-100x what you have available with CMUcam or AVRcam.

Title: Re: confused about blackfin-axon
Post by: Admin on November 30, 2009, 10:53:09 AM

hgordon, the reason I was confused about the Blackfin having ADC is that the datasheet says

"These modes support ADC/DAC connections, as well as video
communication with hardware signalling."

But it didn't say any more. Various forums talk about the Blackfin having a 25MHz ADC . . . possibly a different chip model?

Title: Re: confused about blackfin-axon
Post by: hgordon on November 30, 2009, 05:35:57 PM

There is a BF525C that had a built-in stereo audio codec, but I don't know of any other Blackfins that include analog support.  However, they have a high-speed DMA interface called SPORT that can be easily connected to a family of ADCs and DACs.  That might be what is implied.  We use the AD7998 with the Blackfin - it is an 8-channel 12-bit ADC that easily interfaces via I2C, but it's not that fast.