Onion Omega2S / 2S+ a Linux computer module was launched specifically for IoT (OEMs) applications. Omega2S feature interfaces like USB, SDHC/eMMC storage support, Ethernet, 3x UARTs, I2C, SPI, I2S, GPIOs, etc.
The cost of the module is very attractive. Many engineers would like to use this module for their embedded product development. But, there are various limitations which one needs to be aware of before making a decision on using it.
What are the various advantages of this Linux computer module which has become so popular?
Various advantages of Onion Omega2S computer module
1. Small Form Factor
It is a small 34x20x2.8 mm package. One can use it for a product with size constraints.
2. Castellated Pads
It has half-cut edge pads, you can solder it on the application PCB directly. No connector required. Also, one can hand-solder it easily during the prototyping phase.
3. Low Cost
On Mouser.com for a single unit, Omega2S costs only 11.05$ & Omega2S+ costs 12.21$.
4. Inbuilt WiFi
It has inbuilt WiFi with U.FL connector for an external antenna. Option for an external antenna very useful. Many times the PCB antenna is not enough for the performance required in the field.
5. Documentation Support
Good amount of online documentation and forum support is available.
Onion Omega2S module is available on Mouser and Digikey for purchase in low quantities. For direct purchase min. order quantity is 250 units. For smaller quantities, Onion recommends purchasing from Mouser.com. Mouser provides more cost-effective shipping options.
Given the cost, Single core MIPS 580Mhz CPU, Flash (64MB/128MB) and RAM (16MB/32MB) are quite decent. It has pins for USB, SDHC/eMMC storage support, Ethernet, 3x UARTs, I2C, SPI, GPIOs, I2S, etc.
The module is CE/FCC certified. So, the developer need not worry about EMI issues.
Now, let us see what are the limitations of this little low cost embedded Linux computer module.
Limitation of Onion Omega2S computer module
This is the most critical parameter. As per the Onion website, guaranteed availability is till Jan 2022. That’s a big limitation. In general, a product needs 18-24 months of time to be ready for the market. And then, atleast 2-3 years for selling the product. For this reason, a module should have a min availability of 7 years. The company might claim that availability might get extended but still, there is a big risk.
2. Temperature Range
Its operating temperature is -10 to 55 Degree C. Many Commercial/Industrial applications will need a wider operating temperature range.
3. Limited CPU performance
It has a single core MIPS processor running at 580Mhz. Might not be good enough for complex applications.
4. Limited Flash & RAM
It has Flash memory of 64MB/128MB and RAM of 16MB/32MB which is also suitable only for small applications.
5. No Display Interface
There is no RGB/LVDS/VGA/HDMI display interface available on the pins. One needs to use other interfaces or PCIe based converter to attach any TFT display.
6. Low IO count
It has one I2C, one SPI, one Ethernet, one USB 2.0, 3x UARTs (only RX, TX), one SDHC/eMMC, one I2C, and few more GPIOs. This is quite a limited IO count for a commercial application. One USB port is also not enough. If you want to connect external USB devices like keyboard, mouse, wireless modules, etc. and some internal USB device, you will need more than one USB ports.
7. UART with no flow control
Omega2S module cannot interface with the devices which need UART flow control. One such example is wireless modems where RX, TX, RTS, CTS pins are required.
8. Hardware / Firmware limitations
Go through the forums and limitation section to know various bugs/hardware limitation. Read this & this.
Conclusion: Temperature range and other IO count limitation might be ok for some applications, but, the availability of the Omega2S module is the biggest issue. So the Omega2S module is suitable only for the experiments or hobby projects until availability is guaranteed by the manufacturers else it is risky.
Hope, this information helps.
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Happy learning to you!
Hope you would entertain responses other than “Great Post” sort.
First of all, we need to understand the area onion omega is focusing on. It is a miniature Linux computer. We can’t compare it with Raspberry Pi sort of SBCs. O2 consumes 220mW with WiFi ON, and only 110-120mW with WiFI OFF. RPi & many SBCs consume 4 times r more power. O2 is meant to be programmed to do one or may be a few tasks (read, sensors) just like the UNIX applications’ principle. Do one task; do that extremely well. Most people buy the S (castellated) version and design own PCB around it, and roll out a product with a handful of sensors mounted on the board (and interfaced to the Omega). That is how businesses use products. Businesses prefer not to use RPi sort of “single board computers”; hobbyists and students prefer SBCs mostly. We can’t knockdown an RPi and build a custom board around the Broadcom chip, can we? Last year RPi introduced RP2040 chip that is meant for “custom PCB”, but it is Cortex-M not an A as in the case of traditional RPi. One needs to think about every aspect before saying, oh, it does not have HDMI, it has only one I2C, it has only one USB. Most IoT applications doesn’t even require USB/HDMI at all. If you visit O2 forum, you can read posts made by people who run a business around O2. Some of them use 100s while some others use 1000s If you go to Arduino or RPi forums, are there any running 1000s of those boards?
What would you comment on Dilaog DA16200, a new CortexM4F WiFi chip/SoC? It has single core 512kB RAM, 4MB Flash. Dialog only offers QFN module, not even castellated. There are people excited about DA16200.
BTW, Omega2 prices have go up recently & there was acute shortage.
Great post, This is really a useful info!!