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In 2012, EE Times reported that IS2T’s MicroEJ platform included MicroJvm, a Java virtual machine said to use 28 KB of flash and less than 1.5 KB of RAM. Those are historical, configuration-specific runtime figures—not the memory needed for a complete Java application or graphical interface.
What does the 28 KB figure include?
The figure describes the MicroJvm runtime, not an entire embedded product. EE Times reported the 28 KB flash and less-than-1.5 KB RAM figures, along with a 2 ms boot time at 120 MHz, as IS2T figures in its November 5, 2012 article, “28KB Java virtual machine supports 32-bit MCUs”. These were reported claims, not an independent benchmark.
A separate 2013 ARM technical document described a minimum MicroJvm requirement of 28 KB flash and 1 KB SRAM, excluding application code. The numbers differ because the sources describe the system in different terms and configurations; they should not be combined into one universal specification. MicroEJ vendor demonstration pages also state 28 KB flash and 1.5 KB RAM for the VM, but the publication date is not shown on those pages: Efficient GUI Development on Cortex-M4 with MicroEJ and Email Client Java App Embedded Into A STM32F434 Board.
Application code, libraries, graphics assets, and any operating-system components require additional memory. As a scale comparison, EE Times reported that an advanced graphical HMI required 90–140 KB of total program memory. That is a reported figure for the described HMI, not a universal MicroEJ system requirement.
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- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
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Why can the runtime be small?
The ARM-hosted explanation describes a build model in which Java objects are preprocessed and linked on a desktop before the resulting program is loaded onto the microcontroller. In other words, much of the work needed to turn the Java application into something deployable happens off the MCU rather than through a full desktop-style Java runtime running on the device. The ARM document sets out this approach and its constraints in The many ways of programming an ARM Cortex-M microcontroller.
This helps explain why a small VM footprint does not mean arbitrary Java software will fit. A project still needs to account for the linked application, libraries, graphics, and other platform components in its target memory budget.
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What is the trade-off for loading code?
In the off-board preprocessing and linking arrangement described by ARM, runtime downloading of Java bytecode objects is not available. That is important if a product must install new application code after deployment without rebuilding and reflashing the firmware through its supported update process.
Before choosing this model, establish how software updates will work in the field. If dynamic installation of Java code is a requirement, confirm directly with the vendor whether a supported configuration meets it; the cited ARM description does not provide that capability.
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How does deployment and debugging fit in?
EE Times described MicroEJ deployments on Cortex-M3 and Cortex-M4 targets and mentioned JTAG or another in-system programming method. JTAG is a deployment/debugging route, not a guarantee that any debugger will work with every board. Select tools only after checking the MCU board’s debug interface and the project’s toolchain.
The same EE Times article said configurable Cortex-M3/M4 platforms were expected from December 11, 2012. That date and the article’s evaluation and licensing details are historical; they do not establish current availability, pricing, licensing, or support.
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- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
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What to verify before using it on an MCU
- Total memory: Budget for the VM and the actual application, libraries, graphics, and operating-system components—not just the runtime figure.
- Target fit: Confirm support for the specific MCU, RTOS, and toolchain combination.
- Application requirements: Identify the graphics and Java libraries the product needs, then establish their contribution to the built image.
- Update model: Decide whether desktop preprocessing and linking followed by device programming is acceptable, or whether runtime code downloads are essential.
- Development workflow: Check the board’s debug and programming interfaces before selecting JTAG or other tools.
- Commercial terms: Verify current product availability, licensing, and support directly with MicroEJ; the 2012 report does not establish today’s terms.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
