The Raspberry Pi Compute Module 3 Lite (CM3L) is a DDR2-SODIMM-mechanically-compatible System on Module (SoM) containing processor, memory and supporting power circuitry. The module allows a designer to leverage the Raspberry Pi hardware and software stack in their own custom systems and form factors. In addition the module has extra IO interfaces over and above what is available on the Raspberry Pi model A/B boards opening up more options for the designer.

The CM3L contains a BCM2837 processor (as used on the Raspberry Pi 3) and 1GB LPDDR2 RAM. The CM3L product is the same as CM3 except the eMMC Flash is not fitted, and the SD/eMMC interface pins are available for the user to connect their own SD/eMMC device.

Note that the BCM2837 processor is an evolution of the BCM2835 processor (as used on the original Raspberry Pi and Raspberry Pi B+ models, as well as the first iteration of the Compute Module). The only real differences are that the BCM2837 can address more RAM (up to 1GB) and the ARM CPU complex has been upgraded from a single core ARM11 in BCM2835 to a Quad core Cortex A53 with dedicated 512KB L2 cache in BCM2837. All IO interfaces and peripherals stay the same and hence the two chips are largely software and hardware compatible.

The pinout of the CM3L is identical to that of the original Compute Module (CM1). Apart from the CPU upgrade and increase in RAM the other significant hardware differences to be aware of are that CM3L has grown from 30mm to 31mm in height, the VBAT supply can now draw significantly more power under heavy CPU load, and the HDMI HPD N 1V8 (GPIO46 1V8 on CM1) and EMMC EN N 1V8 (GPIO47 1V8 on CM1) are now driven from an IO expander rather than the processor. If a designer of a CM1 product has a suitably specified VBAT, can accomodate the extra 1mm module height increase and has followed the design rules with respect to GPIO46 1V8 and GPIO47 1V8 then a CM3L should work fine in a board designed for a CM1.

The Compute Module 3 contains the guts of a Raspberry Pi 3 (the BCM2837 processor and 1GB RAM) as well as a 4GB eMMC Flash device (which is the equivalent of the SD card in the Pi). The Pi 3 has a processor speed of 1.2GHz and runs at roughly 10 times the speed of the Pi 1 due to its quad-core CPU. This is all integrated on to a small 67.6mm x 31mm board which fits into a standard DDR2 SODIMM connector (the same type of connector as used for laptop memory). The Flash memory is connected directly to the processor on the board, but the remaining processor interfaces are available to the user via the connector pins. You get the full flexibility of the BCM2837 SoC (which means that many more GPIOs and interfaces are available as compared to the Raspberry Pi), and designing the Module into a custom system should be relatively straightforward as we’ve put all the tricky bits onto the Module itself.

The Compute Module is available for purchase in single units, or in batches of hundreds or thousands. To get started designing a PCB to use the Module, we provide an open-source breakout board with a single Module in an affordable development kit.

A lite version of the Compute Module 3 is also available. The CM3L brings the SD card interface to the Module pins so a user can wire this up to an eMMC or SD card of their choice.