Raspberry Pi 4 Compute Module

Sajjad Hussain
Oct 26 · 5 min read

After more than a year, industrial developers finally waited for the Raspberry Pi 4 computing module, namely the Raspberry Pi 4 Model B.

For each generation of embedded computer Raspberry Pi (Raspberry Pi), the official will release the same architecture computing module after the basic version is launched for a period of time. The Raspberry Pi 1 computing module was launched in 2014, and the Raspberry Pi 3 and 3+ were updated in 2017 and 2019 respectively. Only the shortest-lived Raspberry Pi 2 has not received such a version.

Sixteen months have passed since the release of the Raspberry Pi 4, which claims to have achieved “PC-level” performance, in June 2019. Today, the Raspberry Pi development team announced the launch of Compute Module 4, starting at $25.

“Of the more than 7 million Raspberry Pi devices sold each year, more than half will be used for commercial purposes, from electronic tags, simple clients to process automation systems,” said Eben Upton, founder of the Raspberry Pi Foundation The product release blog said. “People often prefer to use Raspberry Pi for single-chip microcomputer applications, but for users who need more compact, or specific environments, and on-board eMMCC storage, the computing module can provide a form between the original Raspberry Pi and mass production. .”

Significantly improved performance

The Raspberry Pi Compute Module 4 (CM4) is built on the same 64-bit quad-core Broadcom BCM2711 processor as the Raspberry Pi 4, and its performance has improved a lot compared to the previous generation it. There are faster CPU cores, better multimedia performance, more excuses, and for the first time you can choose a variety of RAM capacity and wireless network connection methods. At the same time, like Raspberry Pi 4, the new computing module can support two 4K computer screens through dual HDMI interfaces to achieve a 60-frame refresh rate display.

The official listed the basic configuration information of the Raspberry Pi 4 computing module:

  • 1.5GHz quad-core Arm Cortex-A72 CPU
  • VideoCore VI graphics card, supporting OpenGL ES 3.x
  • 4k 60-frame hardware decoding, support H.265 (HEVC)
  • 1080p 60-frame hardware decoding, and 1080p 30-frame hardware decoding, supporting H.264 (AVC)
  • Dual HDMI interface, resolution up to 4K resolution
  • Single channel PCI Express 2.0 interface
  • Dual MIPI DSI display and dual MIPI CSI-2 camera interface
  • 1GB, 2GB, 4GB and 8GB LPDDR4–3200 SDRAM memory
  • Optional 8GB, 16GB, 32GB eMMC flash memory
  • Optional 2.4GHz and 5GHz IEEE 802.11b/g/n/ac wireless LAN and Bluetooth 5.0
  • With Gigabit Ethernet PHY and IEEE 1588 support
  • 28 GPIO pins, as well as 6 UART interfaces, 6 12C interfaces and 5 serial peripheral interface bus SPI

The previous generation Raspberry Pi Compute Module 3 (CM3) has the same 1.2GHz quad-core Broadcom BCM2837 processor as Pi 3 Model B, VideoCore IV GPU and 1GB memory. In contrast, the performance improvement of the new generation of products is about 3 times.

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Raspberry Pi 4 computing module Lite version, model without eMMC flash memory.

New appearance, more compact

It must be noted that the Raspberry Pi 4 computing module introduces a brand-new form factor, which interrupts compatibility with the previous modules. The previous module adopted the JEDEC DDR2 SODIMM mechanical standard with I/O signals on the edge connector. Now the I/O signals of the new Raspberry Pi are located on two high-density orthogonal connectors (one for power and low-speed Interface, one for high-density interface).

This design significantly reduces the overall size of the module (the new size is 55mm×40mm), which can make your final product smaller. Compared with the previous computing module, the Raspberry Pi 4 computing module changes because of the shape change, which means that you need a new Compute Module IO board to use all the interfaces for development. The latter costs $35.

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The high-density connector on the reverse side of the development board.

32 variants

Because the computing module this time has a variety of RAM, flash memory and wireless connection options, there are 32 different versions in total. The price also ranges from US$25 (1GB RAM, no WIFI function) up to US$90 (8GB RAM, 32GB flash memory plus WIFI function).

The four basic 1GB RAM models in the new series are the same as the Raspberry Pi 3+ computing module ($25, 30, 35 and 40 respectively).

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The “base” of the Raspberry Pi: CM4 IO board

At the same time, Raspberry Pi officially launched a new IO board, providing users with a ready-made development platform and design starting point.

Its configuration includes:

  • Two regular size HDMI ports;
  • Gigabit Ethernet socket;
  • Two USB 2.0 ports;
  • MicroSD card socket (only Lite, no-eMMC Compute Module 4 models);
  • PCI Express Gen 2 x1 socket;
  • HAT footprint and PoE interface with 40-pin GPIO connection;
  • Barrel jack 12V input (supports up to 26V without PCIe)
  • Camera and display FPC connection;
  • With battery real timer.

IO board CAD adopts KiCad format, users can use this feature-rich open source PCB layout package to design their own calculation modules. The official also gave an operating manual.

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CM4 installed on the IO board.

The price of this IO board is 35 US dollars. In general, a complete software package with computing modules starts at 60 US dollars.

CM4 antenna kit

Generally speaking, most users of wireless CM variants can rely on the PCB antenna of the motherboard to meet their use needs, but in some cases they cannot, such as the product is a metal shell, or the necessary ground plane cutting cannot be achieved under the module. An external antenna is required.

The antenna kit of CM4 includes an antenna, a screw fixing and a U.FL connector connected to the module interface.

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Antenna kit and CM4.

All in all, CM4 has the same functions as Raspberry Pi 4 Model B, but adopts a more flexible and slightly more complicated form. From 1 GB to 8 GB, from 25 US dollars to 90 US dollars, users can choose as many as 32 specifications, so that it sounds like eating hot pot-with the bottom of the pot, you can freely choose the side dishes.

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