I need to put out a VGA signal from an AT91SAM7SE512. How can I do this without using an extra controller? I saw stuff on the web, but it needs to be able to modify the specific pixels.
A:
Unless your ARM7 has some kind of controller, capable of reading memory and outputting video signal without CPU intervention, ie some kind of framebuffer, I don't think you can do that with an ARM7. Well, you probably can, but not within a general purpose OS like linux.
What you can do is transform your ARM7 into a VGA dedicated controlleur, that spends its time launching dma transfer from SDRAM to an external bus. This will IMO not leave a lot of resource to do anything else.
shodanex
2010-02-02 15:45:59
+1
A:
You could probably use something similar to old tricks to make NTSC signals with PWM it will probably look horrible. A better bet is to get some form of video controller even a cheap low resolution one.
Matthew Whited
2010-02-02 16:01:55
Well, could I connect an FPGA to an ARM or make the FPGA read from an SDRAM that the ARM writes to?
Tristan Seifert
2010-02-03 02:21:23
A FPGA is just a programmable logic cell chip. You may attach it to anything you want with as many I/O pins as you want. You can even use them to simulate/emulate finite state machines (CPUs.) If you want to attach it directly to the SDRAM you will need a memory controller (which could also be a FPGA) to switch between the ARM and the FPGA. The ARM would upload memory pages and the FPGA would download those pages. You would probably also want an external clock such as a crystal. Unless you are doing this as a "learning experience" I would really recommend a real video controller.
Matthew Whited
2010-02-04 16:06:03
A:
Your ARM chip has an ADC. It doesn't have a DAC, though. VGA is an multiple-channel analog output, so you need some kind of DAC, and in turn an external component. Another problem you might encounter is the need for proper drivers (the electronic kind, not sofware). A VGA cable can be quite long, which means you have large capacities to overcome, plus it may work as an antenna.
MSalters
2010-02-02 16:28:07