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DOCUMENTATION > HARDWARE > RASPBERRYPI > SCHEMATICS

SCHEMATICS

Schematics for the various Raspberry Pi board versions:

MODEL B+

MODEL A AND B



RASPBERRY PI HARDWARE

The hardware in the Raspberry Pi

  • Schematics
    • Schematics for the Raspberry Pi Model A, B and B+
  • BCM2835/BCM2836
    • The Broadcom processors used in Raspberry Pi
  • Mechanical Drawings
    • Mechanical drawings of the Raspberry Pi Model B+
  • Power
    • Powering the Raspberry Pi
  • USB
    • USB on the Raspberry Pi
  • GPIO
    • General Purpose Input/Output pins on the Raspberry Pi
  • SPI
    • SPI on the Raspberry Pi



RASPBERRY PI DOCUMENTATION

This is the official documentation for the Raspberry Pi, written by the Raspberry Pi Foundation with community contributions.

CONTENTS

  • Setup / Quickstart
    • Getting started with your Raspberry Pi, including what you need and how to get it booted
  • Installation
    • Installing an operating system on your Raspberry Pi
  • Usage Guide
    • Explore the desktop and try out all the main applications
  • Configuration
    • Configuring the Pi's settings to suit your needs
  • Remote Access
    • Accessing your Pi remotely via SSH, VNC or over the web
  • Linux
    • Fundamental Linux usage for beginners and more advanced information for power users
  • Raspbian
    • Information about the recommended operating system for Raspberry Pi
  • Hardware
    • Technical specifications about the Raspberry Pi hardware and the camera module
  • Troubleshooting
    • Got a problem with your Pi? Start here

CONTRIBUTIONS

If you have anything to fix or details to add, first file an issue on GitHub to see if it is likely to be accepted, then file a pull request with your change (one PR per issue).

This is not intended to be an open wiki; we want to keep it concise and minimal but will accept fixes and suitable additions.

See our contributing policy.

LICENCE

Unless otherwise specified, everything in this repository is covered by the following licence:

Creative Commons Attribution-ShareAlike 4

Raspberry Pi Documentation by the Raspberry Pi Foundation is licensed under aCreative Commons Attribution 4.0 International Licence.

Based on a work at https://github.com/raspberrypi/documentation









Compute Module Hardware Design Guide

Powering the module

The Compute Module has six separate supplies that must be present and powered at all times; you cannot leave any of them unpowered, even if a specific interface or GPIO bank is unused. The six supplies are as follows:

  1. VBAT is used to power the BCM2835 processor core. It feeds the SMPS that generates the chip core voltage.
  2. 3V3 powers various BCM2835 PHYs, IO and the eMMC Flash.
  3. 1V8 powers various BCM2835 PHYs, IO and SDRAM.
  4. VDAC powers the composite (TV-out) DAC.
  5. GPIO0-27_VREF powers the GPIO 0-27 IO bank.
  6. GPIO28-45_VREF powers the GPIO 28-45 IO bank.
SupplyVoltage / Voltage RangeTolerance
VBAT2.3-5V [1]+/- 5%
3V33.3V+/- 5%
1V81.8V+/- 5%
VDAC2.5-2.8V (can connect to 3V3 if unused)+/- 5%
GPIO0-27_VREF1.8-3.3V+/- 5%
GPIO28-45_VREF1.8-3.3V+/- 5%

[1] Note that the voltage range for best SMPS efficiency is ~3.3-4.3V.

Power sequencing

Supplies must be synchronised to come up at exactly the same time. Alternatively, they should be staggered so that the highest voltage comes up first, then the remaining voltages in descending order. This is to avoid forward biasing internal (on-chip) diodes between supplies, and causing latch-up.

Power requirements

Exact power requirements will be heavily dependent upon the individual use case. If an on-chip subsystem is unused, it is usually in a low power state or completely turned off. For instance, if your application does not use 3D graphics then a large part of the core digital logic will never turn on and need power. This is also the case for camera and display interfaces, HDMI, USB interfaces, video encoders and decoders, and so on.

Powerchain design is critical for stable and reliable operation of the Compute Module. We strongly recommend that designers spend time measuring and verifying power requirements for their particular use case and application, as well as paying careful attention to power supply sequencing and maximum supply voltage tolerance.

The following table gives a rough guide to minimum supply requirements. However, the user is responsible for verifying that their powerchain is designed to be sufficient for their application. In some more unusual use cases these minimum requirements may well be too low!

SupplyMinimum Requirement (mA or mW)
VBAT2000mW [1]
3V3250mA
1V8250mA
VDAC25mA
GPIO0-27_VREF50mA [2]
GPIO28-45_VREF50mA [2]

[1] Note that VBAT is heavily dependent upon the application. For example, with video encoding, 3D and the camera all running the power requirements can be substantial.

[2] Note that each GPIO bank will only need a few mW if unused; however when in use, the requirements will vary depending on the number of IOs in use and the load on each. The maximum load per GPIO bank must not exceed 50mA.

Module booting and flashing the eMMC

The 4GB eMMC Flash device on the Compute Module is directly connected to the primary BCM2835 SD/eMMC interface. These connections are not accessible on the module pins.

When initially powered on, or after the RUN pin has been held low and then released, the BCM2835 will try to access the eMMC device. It will then look for a file called bootcode.bin on the primary partition (which must be FAT) to start booting the system. If it cannot access the eMMC device or the boot code cannot be found, it will fall back to waiting for boot code to be written to it over USB; in other words, its USB port is in slave mode waiting to accept boot code from a suitable host.

A USB boot tool is available on github which allows a host PC running Linux to write the BCM2835 boot code over USB to the module. That boot code then runs and provides access to the eMMC as a USB mass storage device, which can then be read and written using the host PC. Note that a Raspberry Pi can be used as the host machine.

The Compute Module has a pin called EMMC_DISABLE_N which when shorted to GND will disable the eMMC, forcing BCM2835 to boot from USB. Note that when the eMMC is disabled in this way, it takes a few seconds from powering up for the processor to stop attempting to talk to the eMMC device and fall back to booting from USB.

Note that once booted over USB, BCM2835 needs to re-enable the eMMC device (by releasing EMMC_DISABLE_N) to allow access to it as mass storage. It expects to be able to do this by driving the GPIO47_1V8 pin LOW, which at boot is initially an input with a pull up to 1V8. If an end user wishes to add the ability to access the eMMC over USB in their product, similar circuitry to that used on the Compute Module IO Board to enable/disable the USB boot and eMMC must be used; that is, EMMC_DISABLE_N pulled low via MOSFET(s) and released again by MOSFET, with the gate controlled by GPIO47_1V8. Ensure you use MOSFETs suitable for switching at 1.8V (i.e. use a device with Vt << 1.8V).

For a step by step guide to flashing the eMMC please see here

Compute Module interfaces

GPIOs

Note that the GPIO46_1V8 and GPIO47_1V8 pins are 1.8V IO only and are reserved for special functions (HDMI hot plug detect and boot control respectively). Please don’t use these pins for any other purpose, as the software for the Compute Module will always expect these pins to have these special functions. If they are unused please leave them unconnected.

The remaining GPIOs are available for general use and are split into two banks. GPIO0 to GPIO27 are bank 0 and GPIO28-45 make up bank 1. GPIO0-27_VREF is the power supply for bank 0 and GPIO28-45_VREF is the power supply for bank 1. These supplies can be in the range 1.8V-3.3V. These supplies are not optional; each bank must be powered, even when none of the GPIOs for that bank are used.

All GPIOs except GPIO28, 29, 44 and 45 have weak in-pad pull-ups or pull-downs enabled when the device is powered on. Whether the GPIO is pulled up or down is documented in the BCM2835 peripherals document section 6.2. It is recommended to add off-chip pulls to GPIO28, 29, 44 and 45 to make sure they never float during power on and initial boot.

CSI (MIPI serial camera)

The Compute Module has two MIPI serial camera interfaces (CSI); Interface 0 and Interface 1.

Interface 0 is a 2-lane interface; one clock lane and two data lanes.

Interface 1 is a 4-lane interface; one clock lane and four data lanes.

Note that the Raspberry Pi Model A/B camera connector uses Interface 1, but only in a 2-lane configuration.

The camera interface(s) clock and data pins must be routed as matched length, matched phase 100 ohm differential PCB traces.

DSI (MIPI serial display)

The Compute Module has 2 MIPI serial display interfaces (DSI); Interface 0 and Interface 1.

Interface 0 is a 2-lane interface; one clock lane and two data lanes.

Interface 1 is a 4-lane interface; one clock lane and four data lanes.

Note that the Raspberry Pi Model A/B display connector uses Interface 1, but only in a 2-lane configuration.

The display interface(s) clock and data pins must be routed as matched length, matched phase 100 ohm differential PCB traces.

USB OTG

The BCM2835 USB port is On-The-Go (OTG) capable. If using either as a fixed slave or fixed master, please tie the USB_OTGID pin to ground.

The USB port (Pins USB_DP and USB_DM) must be routed as matched-phase 90 ohm differential PCB traces.

Note that the port is capable of being used as a true OTG port, but there is currently no documentation, code or examples for this use case.

HDMI

It is recommended that users follow a similar arrangement to the Compute Module IO Board circuitry for HDMI output.

The HDMI CK_P/N (clock) and D0-D2_P/N (data) pins must each be routed as matched length 100 ohm differential PCB traces. It is also important to make sure that each differential pair is closely phase matched. Finally, keep HDMI traces well away from other noise sources and as short as possible.

Failure to observe these design rules is likely to result in EMC failure.

Composite (TVDAC)

The TVDAC pin can be used to output composite video. Please route this signal away from noise sources and use a 75 ohm PCB trace.

Note that the TV DAC is powered from the VDAC supply which must be a clean supply of 2.5-2.8V. It is recommended users generate this supply from 3V3 using a low noise LDO.

If the TVDAC output is not used VDAC can be connected to 3V3, but it must be powered even if the TV-out functionality is unused.

Compute Module temperature range

The operating temperature range of the module is set by the lowest maximum and highest minimum of any of the components.

The Samsung eMMC and Samsung LPDDR2 are all rated for -25 to +80 degrees Celsius, so the range is -25 to +80. BCM2835 and the analogue switch have a greater range; the ceramic capacitors are specified from -25 to +85.

However, this range is the maximum for the silicon die; therefore, users would have to take into account the heat generated when in use and make sure this does not cause the temperature to exceed 80 degrees Celsius.

The user is responsible for designing and testing their system so that these limits are not exceeded.

Compute Module form factor

The Compute Module conforms to JEDEC MO-224 mechanical specification for 200 pin DDR2 (1.8V) SODIMM modules. Please note that the pinout of the Compute Module is not the same as a DDR2 SODIMM module; they are not electrically compatible.

The maximum component height on the underside of the Compute Module is 1.2mm.

The maximum component height on the top side of the Compute Module is 1.5mm.

The Compute Module PCB thickness is 1.0mm +/- 10%.

Note that the location and arrangement of components on the Compute Module may change slightly over time due to revisions for cost and manufacturing considerations; however, maximum component heights and PCB thickness will be kept as specified.




Compute Module Attaching & Enabling Peripherals Guide

Introduction

This guide is designed to help developers using the Compute Module get to grips with how to wire up peripherals to the Compute Module pins, and how to make changes to the software to enable these peripherals to work correctly.

The Compute Module contains the Raspberry Pi BCM2835 System On Chip (SoC) or "processor", memory and eMMC (eMMC is basically like an SD card but soldered onto the board, eMMC (unlike SD cards) is specifically designed to be used as a disk and has extra features that make it more reliable in this use case). Most of the pins of the SoC (GPIO, 2 CSI camera interfaces, 2 DSI display interfaces, HDMI etc.) are freely available and can be wired up as the user sees fit (or if unused can usually be left unconnected). The Compute Module is a DDR2 SODIMM form factor compatible module, so any DDR2 SODIMM socket should be able to be used (note the pinout is NOT the same as an actual SODIMM memory module).

To use the Compute Module a user needs to design a (relatively simple) 'motherboard' that can provide power to the Compute Module (3.3V and 1.8V at minimum) and wires the pins up to the required peripherals for the user's application.

Raspberry Pi provide a minimal motherboard for the Compute Module (called the Compute Module IO Board or CMIO Board) which powers the module, brings out the GPIO to pin headers, brings the camera and display interfaces out to FFC connectors, provides HDMI, USB and an 'ACT' LED as well as the ability to program the eMMC of a module via USB from a PC or Raspberry Pi.

This guide first explains the boot process and how Device Tree is used to describe attached hardware (which are essential things to understand when designing with the Compute Module). It then provides a worked example of attaching an I2C and an SPI peripheral to a CMIO Board and creating the Device Tree files necessary to make both peripherals work under Linux (starting from a vanilla Raspbian OS image).

Note that using Device Tree is the officially supported method of doing things (for both a Compute Module and a Raspberry Pi), you can at the moment turn off device tree in the kernel altogether but we won't be providing support for this.

BCM283x GPIOs

BCM283x has 3 banks of General Purpose Input Output (GPIO) pins (28 pins on Bank0, 18 pins on Bank1 and 8 pins on Bank2; 54 pins in total). These pins can be used as true GPIO (i.e. software can set them as inputs or outputs, read and/or set state and use them as interrupts) but also can be set to 'alternate functions' such as I2C, SPI, I2S, UART, SD card and others.

On a Compute Module both Bank0 and Bank1 are free to use with Bank2 used for eMMC and HDMI hot plug detect and ACT LED / USB boot control.

It is useful on a running system to look at the state of each of the GPIO pins (what function they are set to, and the voltage level at the pin) - so that one can see if the system is set up as expected (this is particularly useful to see if a Device Tree is working as expected or to get a look at the pin states during hardware debug).

Raspberry Pi provide the raspi-gpio package which is a tool for hacking / debugging GPIO (NOTE you need to run it as root). To install raspi-gpio:

sudo apt-get install raspi-gpio

If apt-get can't find the raspi-gpio package you need to do an update first:

sudo apt-get update

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