Rpi Hardware

From eLinux.org
Revision as of 09:11, 16 January 2012 by Alpaca (Talk | contribs)

Jump to: navigation, search
A diagram denoting the places of the different components on the Rpi, made by Paul Beech

Hardware of the Raspberry Pi


(Provisional - some of the expansion interfaces won't be available on production boards) (PCB IDs are those of the Model B Beta board)

  • SoC: Broadcom BCM2835 media processor system-on-chip featuring:
    • CPU core: ARM1176JZF-S ARM11 core clocked at 700MHz; ARM VFP.
    • GPU core: a Broadcom VideoCore IV GPU providing OpenGL ES 1.1, OpenGL ES 2.0, hardware-accelerated OpenVG 1.1, Open EGL, OpenMAX and 1080p30 H.264 high-profile decode. There are 24 GFLOPS of general purpose compute and a bunch of texture filtering and DMA infrastructure. Eben worked on the architecture team for this and the Raspberry Pi team are looking at how they can make some of the proprietary features available to application programmers
    • DSP core: There is a DSP, but there isn't currently a public API (Liz thinks the BC team are keen to make one available at some point)
    • RAM: 128MiB (Model A) or 256MiB (Model B) of SDRAM. The RAM is physically stacked on top of the Broadcom media processor (package-on-package technology)
  • LAN9512 (Data Brief | Data Sheet) providing 10/100Mb Ethernet and 2x USB 2.0 (Model B)
  • S1: Micro USB power jack (5v)
  • S2: DSI interface. 15-pin surface mounted flat flex connector (possibly no-fit).
  • S3: HDMI connector providing HDMI 1.3a out
  • S4: Composite Video connector: RCA
  • S5: MIPI CSI-2 interface. 15-pin surface mounted flat flex connector (possibly no-fit).
  • S6: Audio connector: 3.5mm stereo jack (output only)
  • S8: SD/MMC/SDIO memory card slot (underside)
  • S7: Either 1x USB 2.0 (Model A) 2x USB 2.0 (Model B)
  • P1: 26-pin 2.54mm header expansion (header not fitted), providing:
    • 8 GPIOs at 3v3
    • 2-pin UART serial console, 3v3 TTL (debug); or 2 GPIOs at 3v3
    • I2C interface (3v3); or 2 GPIOs at 3v3
    • SPI interface (3v3); or 5 GPIOs at 3v3
    • 3v3, 5v and GND supply pins
    • ARM JTAG (if pins are reconfigured in software)
    • Second I2C interface (3v3) (if pins are reconfigured in software)
    • I2S interface (if pins are reconfigured in software)
    • 6 pins reserved for future use
  • P2 and P3: 8-pin and 7-pin 2.54mm header expansion (header not fitted), providing:
    • 6-pin GPU JTAG (ARM11 pinout)
  • P4: 10/100Mb RJ45 Ethernet jack (Model B)

  • Board size: 85.60mm x 53.98mm. Overall height expected to be less than 25mm. [1]
  • Weight: <40g? (Alpha board weighs ~55g [2])
  • 6 layer PCB [1]

Schematic / Layout

Power management

The board takes fixed 5V input, (with the 1V2 core voltage generated directly from the input using the internal switch-mode supply on the BCM2835 die). This permits adoption of the micro USB form factor, which, in turn, prevents the user from inadvertently plugging in out-of-range power inputs; that would be dangerous, since the 5V would go straight to HDMI and output USB ports, even though the problem should be mitigated by some protections applied to the input power: The board provides a polarity protection diode, a voltage clamp, and a self-resetting semiconductor fuse.

  • Board A: 5V, 500 mA (2.5W) without any devices connected
  • Board B: 5V, 700 mA (2.5W) without any devices connected
  • As the 5V rail is brought out in the GPIO pins, you can power the Rpi from there too. You should mind however, that those are behind the power circuitry , so you should provide your own.
  • It is possible to power the Rpi from a powered USB hub the Rpi controls, but only on 'dumb' devices, that allow the port to supply the full current without waiting for the usb device to ask for it[1]. As the power input of the Rpi doesn't have its data leads connected, there is no chance for a communication loop of some sorts.
  • POE (power over ethernet) is currently not available for the Rpi (but nobody stops you from taking your soldering iron and doing it yourself)


  1. 1.0 1.1 http://www.raspberrypi.org/archives/344
  2. http://www.raspberrypi.org/?page_id=43&mingleforumaction=viewtopic&t=285.0