覆盆子Pi CM4计算模块(Fig. 1)可能是今年制造商空间最重要的公告之一。新的模块偏离了早期Raspberry Pi计算模块的边缘连接方法。尽管这使CM4与以前的运营商委员会不相容，但请不要担心，还有一个正在等待对这个新模块的压抑需求。
The CM4 sports a pair of 100-pin connectors on the read(Fig. 2)。最大的更改是消除Raspberry Pi 4中包含的USB 3接口。有一个USB 2接口，但是如果您需要USB 3接口，则必须将基于PCI Express的USB 3接口添加到混音中。
The x1 PCI Express (PCIe) Gen 2 interface is the more interesting addition, or rather exposer, as it opens the platform up to significant expansion. The addition of a PCI Express switch would allow a carrier board to implement any number of high-speed interfaces. The limitation of Gen 2 or x1 isn’t that significant, as the performance of the host is the limiting factor rather than the size of the pipe.
PCIE接口可用于添加USB 3支持。但是，它还可以打开NVME存储的使用以及访问任何数量的基于PCIE的外围设备（例如其他以太网接口）。
CM4有很多版本,开始with one at $25 that skip things like Wi-Fi 802.11b/g/n/ac and Bluetooth 5.0 support. All versions include the Broadcom BCM2711, which is a 1.5-GHz, 64-bit, quad-core Arm Cortex-A72 processor. Memory and storage are the other factors that change up to 8 GB of LPDDR4-3200 DRAM and 34 GB of eMMC flash memory.
包含CSI-2摄像头界面以及双HDMI接口，使此有趣的平台用于数字签名应用程序。H.265支持4K60解码，H.264支持处理1080P60解码和1080P30编码。还有双DSI MIPI串行显示接口。
The wireless support includes a switch-selectable on-module antenna. This is handy for very small systems that may not need the range provided by an external antenna. Developers should check out纽瓦克的SC0480天线套件如果他们需要其他无线范围或性能(Fig. 3)。纽瓦克还提供CM4的所有版本。
Most of the pins on the two headers are for GPIO, along with the usual smattering of I2C, SDIO/eMMC, and analog found on the usual Raspberry Pi header.
Industrial Design
Use of two low-profile connectors is a good starting point. With its four mounting holes, the module can be locked down tight, which is critical for rugged applications. Prior versions weren’t as rugged. The module design is also more amenable to cooling, although the chips can be used with no heatsink at all depending on the application.
The compact size is also a benefit in embedded applications. The 55- × 40-mm module can easily be mounted atop a small stack of boards or a small carrier board for a very compact design. I wouldn’t be surprised to see a carrier board with one or more M.2 connectors on the flip side, providing high-speed interfaces and storage.
CM4 Carrier Boards
Various carrier boards are already on the market for the CM4, but the standard CM4IO Board is typical(Fig. 4)。It exposes all of the interfaces via connectors and even includes a Raspberry Pi HAT connector. This makes it possible to link the module to the plethora of Raspberry Pi expansion modules that have fomented the platform’s popularity. It even has a x1 PCI Express connector.
All CAD files are readily available in case you want to design your own carrier board. Keep in mind that this can be a bit more challenging than in the past due to the high-speed interfaces, although some existed on earlier compute modules as well. There are 90- and 100-Ω differential pairs on the connectors.
总体而言，系统设计相对简单。该系统仅需要3.3和12-V功率。以太网具有电力欧洲（POE）保护，但没有通常在运营商委员会上找到的支持。
I did want to mention theGumstixRaspberry Pi CM4 + Pixhawk FMUv6 board(Fig. 5)。This is aPixhawk-compatible flight-management-unit (FMU)运行许多FMU软件框架的平台PX4。A similar platform is used forNXP半导体Hovergames。The FMU can operate in a standalone mode, but it’s often paired with a host processor, in this case the CM4.
Gumstix载体板基于STmicroelectronics’ STM32F7 microcontroller. It features a 3D accelerometer and magnetic sensor, camera connectors for the CM4, a CAN transceiver, a MicroSD card slot, 32 KB of FRAM, and USB connectors.
The Gumstix board was designed using its web-basedGeppetto设计工具和服务。可以使用此工具建造板，并在几周内交付了完全填充的硬件。通常有1999美元的设置费，但在2020年底之前，基于CM4的董事会将被取消。
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