5 ms·
Which bus exactly? Reading the BCM2835 datasheet ( http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf http://www.raspberrypi.org/
by pja 12y ago
Which bus exactly? Reading the BCM2835 datasheet ( http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM283... ) the chip has a couple of UARTS, 2 SPI interfaces and a USB interface.
The only interface that can do DMA is the USB one. All the others have relatively small FIFO buffers and require the CPU to do all the I/O work. So you could attach an ethernet interface to one of the SPI buses, or bit bang a few GPIOs but surely the CPU load is going to be painful?
Edit: Oh wait, there's a main SPI bus that can do DMA as well. See page 148 on the doc linked above. If you can find a suitable chipset & driver then have at it :)
- userbinator 12y agoThe internal bus - AMBA/AXI/etc., so it's basically another peripheral block the CPU can access directly. (That datasheet is also very incomplete - there's lots of other interesting stuff in the SoC like the MIPI CSI/DSI interface, and if you felt perverse enough and had the right skillset you might be able to get Ethernet-like data transfer out of one of those...)
- someperson 12y agoSome people appear to have used the SPI bus to attach a new Ethernet port to a Raspberry Pi: http://www.raspberrypi.org/forums/viewtopic.php?f=44&t=18397 http://www.raspberrypi.org/forums/viewtopic.php?f=44&t=18397