Archive for August, 2010
I came up with this problem when I was doing my project. There are more than 66 parallel pinouts on the Spatial Light Modulator (SLM) chip to be controlled. I generated the commands on the computer and then send them to the fpga via DMA FIFO. It worked fine when there were only 64 lines. I can transfer a 1D U64 array to the target and then split each U64 data to 64 booleans.
See also the example ‘DMA buffered acquisition’ in LabVIEW 2009.
When there are 66 bits, I just created 2 FIFOs for the first place, one of which was type U64 while another is U8. I found it very hard to synchronize the 2 FIFOs. Some memory (I can’t remember exactly where it came from) recalled me using case structure to decimate the 1D array. So I interleaved the data to a 1D U32 (because there are 32 bits on Bus A and Bus B) array, and decimated them on the fpga side. By doing this I *wasted* 32×3-66=30 bits per command, which is tolerable and flexible.
We set up the order of procceding by creating a type defined enum (Enum ‘Bus B’ in the figure) and telling the state machine which state the next should be. Note that we need to create a for loop in each iteration. Because we want to dequeue the buffer several times to achieve the commands for all lines.
First of all, there are two news from the lab:
I (finally) managed to drive the Spatial Light Modulator (SLM) directly with LabVIEW FPGA. The coding was not really a challendge, for I already implemented it with DAQmx module. And I just transfered the digital output bits to FPGA. The wiring and debugging were the pains in the ass. After I did that, the work is done. So now we can send whatever images to the SLM chip via the computer without interruption, and the delay is minor.
An SLM chip was damaged. I didn’t figure out the reason yet. Since the chip was taken out and left for weeks, the static may damage it. We had been sending +5V TTL to the pinouts of the chip instead of the recommended +3.3V, which might cause problems. And there is a chance we just powered on and off the device too frequently. The SLM is a liquid crystal one. You can consider it as a 2D array of tiny mirrors. We need to keep its DC balance by sending positive and negative images for the same period. Thus a plan is to create a state machine for the SLM. When we are not using it, leave the state idle, in which state the FPGA sends ‘black image’ commands to the SLM continuously.
Following are 2 huge news I heard recently from internet.
1. Artificial life forms evolve basic intelligence Wow, so we can be the god of the computer world now? I believe there is a way we can simulate the human memory, but the intelligence and the evolution? I would like to digg in.
2. Claimed Proof That P != NP I don’t think I’m smart and patient enough to read through the 100-page paper. Actually this paper has not been peer-reviewed yet. So feel free to challenge it.
But I’m shocked by the conclusion anyway. Sorry, but “!=” means “not equal to” here. That’s not a surprise now. But still, i don’t know if it is true.
This idea just came up to my mind some days ago. The thinking was straightforward. I’m buiding cameras for my PhD project and I love (although I really have no idea about it) open source. I googled this term and found a blog of it. Also, a news was released last September telling us there are some people who already developed this stuff.
Well, I’m glad to see it. At least it appoves that this is not a stupid idea, and someone (in U of Stanford!) considers it serious. But the ‘Frankencamera’ is not so cool as I expected. A demo was given showing it can do auto-chop-and-paste thing, or “Photoshop on the camera”. I hardly found it impressive. I’m not saying it’s a dull camera but I don’t want to programme a camera just to do stuffs I can do off-line.
(Sorry if the order is messy. I’m trying to organize my thought.) So in my opinion, the camera I want to develop is a kind of study camera. It’s not advanced and it’s not expensive. The specification might be:
CMOS sensor, 1024*768 pixels, 8~10 bits, C-mount, USB/firewire interface, size less than 10*5*5 cm, with the price less than 100 pounds.
The potential users are teachers, students and fans who want to try their ideas (algorithm) before they buy the expensive instruments. The flexible parts is you can programme to change the exposure time, frame rate, regions of interest, binding pixels or not, gain, or even determine which regions to look at on the fly(which is implemented in my project:)). Assume the way you are looking for your girl friend in the crowd. You keep your eyes focus on the special target, and all the rest people are blur to you. You can use the camera that way to save the bandwidth and the storage space.
That’s about for this post. I’ll carry on talking about what I found existed on open source cameras and the feedbacks I got from my friends and my supervisor.
I would like to thank Otis and Todd for their kind help and comments. Glad to hear from US:).