COMPUTE MODULE OPERATING INSTRUCTIONS
Contents
1. a The 4GByte eMMC Flash device on the Compute module is directly connected to the primary BCM28235 SD eMMC interface These connections are not accessible on the module pins a When initially powered on or after the RUN pin has been held low and then released the BCM2835 will try and access the eMMC he 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 i e its USB port is in slave mode waiting to accept boot code from a suitable host A USB boot tool is available https github com raspberrypi tools tree master usbboot which allows a host PC running Linux to write he 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 written using the host PC Note that a Raspberry Pi can be used as the host machine device and look for a file called bootcode bin on the primary partition which must be FAT to start booting the system If it cannot access a The compute module has a pin called EMMC_DISABLE_N which when shorted to GND will disable the eMMC forcing BCM2835 to boot o 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 wi2. Raspberry Pi COMPUTE MODULE OPERATING INSTRUCTIONS POWERING THE MODULE The Compute Module has 6 separate supplies that must be present at all times i e they must all be powered you cannot leave any of them unpowered even if a specific interface or GPIO bank is unused 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 GPIOO 27_VREF powers the GPIO 0 27 IO bank 6 GPIO28 45_VREF powers the GPIO 28 45 IO bank SUPPLY VOLTAGE VOLTAGE RANGE TOLERANCE VBAT 2 3 5V 1 5 3V3 3 3V 5 1V8 1 8V 5 VDAC 2 5 2 8V can connect to 3V3 if unused 5 GPIO0 27_VREF 1 8 3 3V 5 GPIO28 45 VREF 1 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 or staggered such that the highest voltage comes up first then the next highest etc 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 app
3. boot code to allow access to the eMMC Once complete you will see a new device appear commonly dev sda but it could be dev sdb etc so have a look in dev before running rpiboot so you can see what changes You now need to write a raw OS image e g Raspian http downloads raspberrypi org raspbian_latest to the device Note the following command may take some time to complete depends on the size of the image sudo dd if raw_os_image_of_your_choice img of dev sda bs 4MiB Once the image has been written unplug and re plug the USB and you should see 2 partitions appear for Raspian in dev In total you should see something like dev sda lt Device dev sda1 lt First partition FAT dev sda2 Second partition Linux filesystem The dev sda1 and dev sda2 partitions can now be mounted normally Make sure J4 USB SLAVE BOOT ENABLE is set to the disabled position and or nothing is plugged into the USB slave port Power cycling the IO board should now result in the Compute Module booting from eMMC 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 unused please leave unconnected The remaining GPIOs are avai
4. aspberry Pi Model A B display connector uses Interface 1 but only in a 2 lane configuration a The display interface s clock and data pins must be routed as matched length matched phase 100 ohm differential PCB traces USB OTG a 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 a 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 currently there is no documentation code examples for this use case HDMI a It is recommended to follow a similar arrangement to the Compute Module IO Board circuitry for HDMI output The HDMI CK_P N clock and DO D3_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 a The TVDAC pin can be used to output composite video Please route this signal away from noise sources and using a 75 ohm PCB trace a f 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 NOTE that the TV DAC is powered from the VDAC supply which must be a
5. clean supply of 2 5 2 8V it is recommended to generate this supply from 3V3 using a low noise LDO COMPUTE MODULE TEMPERATURE RANGE a The operating temperature range of the module is set by the lowest maximum of any of the components and the highest minimum of any of the components a The Samsung eMMC and Samsung LPDDR2 are all rated for 25 to 80 degrees C 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 that is the max range for the silicon die so a user would have to take into account the heat generated when in use and make sure this does not cause the temperature to exceed 80C THE USER IS RESPONSIBLE FOR DESIGNING AND TESTING THEIR SYSTEM SUCH 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 a The maximum component height on the underside of the Compute Module is 1 2mm a The maximum component height on the top side of the Compute Module is 1 5mm a 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 manufacturability however maximum component height
6. lable for general use and are split into 2 banks GPIOO to GPIO27 are bank 0 and GPIO28 45 make up bank 1 GPIOO 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 from power 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 initial boot CSI MIPI Serial Camera The Compute Module has 2 MIPI serial camera interfaces CSI Interface 0 and Interface 1 a Interface 0 is a 2 lane interface one clock lane and 2 data lanes a Interface 1 is a 4 lane interface one clock lane and 4 data lanes a Note that the Raspberry Pi Model A B camera connector uses Interface 1 but only in a 2 lane configuration a 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 a Interface 0 is a 2 lane interface one clock lane and 2 data lanes a Interface 1 is a 4 lane interface one clock lane and 4 data lanes Note that the R
7. lication does not use 3D graphics then a large part of the core digital logic will never turn on and need power Similarly for camera display interfaces HDMI USB interfaces video encode decode etc 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 as to minimum supply requirements However the user is responsible for verifying that their power chain is designed sufficient for their application In some more pathological use cases these minimum requirements may well be too low SUPPLY MINIMUM REQUIREMENT MA OR MW VBAT 2000mW 1 3V3 250mA 1v8 250mA VDAC 25mA GPIO0 27_VREF See note 2 GPIO28 45_VREF _ See note 2 1 NOTE VBAT is heavily dependent upon the application E g with video encode 3D and 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 number of IOs in use and the load on each The designer is responsible for calculating or measuring this themselves based on their particular use case MODULE BOOTING FLASHING THE EMMC
8. s and PCB thickness will be kept as specified Raspberry Pi Raspberry Pi Documentation by the Raspberry Pi Foundation is licensed under a Creative Commons Attribution 4 0 International Licence Based on a work at https github com raspberrypi documentation COMPLIANT WITH element14 A Compute Module Devel t Kit ta evelopmen l A NIJ www element14 com legistration www raspberrypi org Des Gee elementiu
9. th 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 EMMC_DISABLE_N pulled low via MOSFET s and released again by MOSFET with gate controlled by GPIO47_1V8 Be careful to use MOSFETs suitable for switching at 1 8V i e use a device with Vt lt lt 1 8V STEPS TO FLASH THE EMMC ON A COMPUTE MODULE USING A COMPUTE MODULE IO BOARD rom USB Note that when the eMMC is disabled like this it takes a few seconds from power up for the processor to give up trying to talk You need a host Linux system a Raspberry Pi will do ON YOUR COMPUTE MODULE IO BOARD Make sure that J4 USB SLAVE BOOT ENABLE is set to the EN position ON YOUR HOST SYSTEM Git can get upset if the date is not set correctly so on a Raspberry Pi you can do a sudo date MMDDhhmm Where MM is month DD day and hh mm hours and minutes respectively Clone the usbboot tool repository and grab libusb sudo git clone depth 1 https github com raspberrypi tools cd tools usbboot sudo apt get install libusb 1 0 0 dev Build the usbboot tool sudo make a Run the usbboot tool and it will wait for a connection sudo rpiboot Now plug the host machine into Compute Module IO Board USB slave port J15 and power on the CMIO board The usbboot tool will see the compute module and send it
Download Pdf Manuals
Related Search