Overview
Raspberry Pi foundation recently launched the Raspberry Pi Compute module 4 with various new features and advantages compared to their earlier version of Raspberry Pi compute module 3+.
It is interesting to understand various advantages of Raspberry Pi Cm 4. Let’s go through all one by one.
Advantages of Raspberry Pi Cm4
1.Improved CPU Performance
The processor used in Raspberry Pi Cm4 is high performing, its a 1.5GHz quad-core 64-bit ARM Cortex-A72 CPU and on the other hand Raspberry Pi Cm3+ has 1.2GHz quad-core, 64-bit ARM Cortex-A53 CPU.
2. Simple Power Supply
Raspberry Pi Cm3/3+ had a very complex power supply requirement which needed 6 different power rails for the module from the carrier board.
In Cm4, I think Raspberry Pi team has seriously consider this limitation and made it simple in Cm4 where you only need single 5V power supply input to power the module.
3. Inbuilt Ethernet PHY
Raspberry Pi Cm3/3+ didn’t have an inbuilt ethernet PHY on the module which need an external USB to Ethernet bridge converter to be used if one needs the Ethernet.
Raspberry Pi cm4 has inbuilt Ethernet PHY and need only RJ45 with Magnetics on the carrier to realize ethernet connectivity.
4. Option for Wi-Fi on the module
Wi-Fi wasn’t there on the earlier version modules, Raspberry Pi Computer Module 4 comes with an option to have Wi-Fi module and this time it has external antenna option as well, this helps improve the signal strength, allows you to use a metallic enclosure. This fits well with the industrial use case.
5. Improved form-factor for thermal performance
As Raspberry Pi Cm3/3+ modules where having SODIMM formfactor there was no proper mechanisim to attach a heat spreader or heat sink for better CPU performance in very high performaing application. One could only attach smaller heat single on the CPU only.
In Raspberry Pi Cm4, the module form-factor allows to install a heat spreader or heatsink to be firmly attached on top of the module as it has 4 mounting holes. This makes a very professional thermal solution.
So, all in all Raspberry Pi Cm4 is a significantly improved computer module. But, there are a few limitations also which one should consider before starting to build products around it.
Limitations of Raspberry Pi Cm4
1. Operating temperature
Raspberry Pi Cm4 can operate in an ambient temperature of -25 to 85 degree but in many situations we need -40 degree operating range so in those case, module could not be used or need make special arrangements to keep inside temperate with in valid operating range.
2. Single USB Interface
Cm4 module has only single USB2.0 high speed interface. This could be a limitation in my applications. In those cases one need to use external USB hub chip like one is used on the development board.
3. No USB3.0
Sadly, Raspberry Pi Cm4 doesn’t have any USB 3.0.
These days many application need USB 3.0 interface to attach external devices with USB 3.0. If you need USB 3.0 interface, you need to add a PCIe to USB 3.0 bridge converter on your carrier board.
4. Availability
Availability continues to remain a concern regarding Raspberry Pi Modules, no matter if Cm3/3+ or Cm4 so, make sure you have understood the availability of your module variant and secured stocks or got assurance from some of the distributors so that when you start selling you product based on Raspberry Pi Cm4, your customer don’t end up facing long lead times.
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