Introducing Antmicro’s open source Myra System-in-Package

System-in-Packages (SiP) are a way of enclosing multiple integrated circuits into a single component package, often used in space-constrained consumer applications like in wearables or cell phones or miniaturized, environment-hardened devices such as satellites or UAVs.

In this article, we will describe our commercial services in creating custom SiPs on the example of Antmicro’s open source Myra SiP, which combines an MCU, FRAM and a USB to UART converter within a single chip that requires only a single USB connection to operate, significantly reducing its form factor when compared to using individual components.

We’ll also describe a simplified version of our Environment Sensor board that was used for bring-up and testing of the SiP. Both that board and the Myra SiP itself along with 3D renders, block diagrams and other components used, are available in our System Designer, illustrating a multi-level hierarchy of hardware (board-SiP-SoC-IP) that can be visually explored in the portal.

The original Environment Sensor hardware

The Environment Sensor, developed to monitor the temperature, humidity and atmospheric pressure within our data centers, is the precursor to the Myra SiP. The Myra SiP packages the processing subsystem of the board and reuses the same sensor components.

The Environment Sensor’s local storage allows for data logging, while the battery backup provides protection against data loss.

As is typical for our open hardware designs, the Environment Sensor comes with a block diagram of the board as well as 3D visualizations created with our open component database and KiCad-Blender flow. We also designed a custom enclosure, ensuring air circulates only over the atmospheric sensors. The main features of this 50x26.5mm board include:

• STMicroelectronics STM32G474CET6 host MCU
• Fujitsu MB85RC1MTPNF-G-JNERE1 128kB external FeRAM for data storage
• Sensirion SHT45 temperature + humidity sensor
• Bosch BME280 temperature + humidity + pressure sensor
• FTDI Chip FT232RQ-REEL USB to UART Bridge
• firmware built in Zephyr RTOS.

On the software side, besides the Zephyr port, we developed a companion Linux application for the server that retrieves environmental data from sensors connected to the device it is being run on. The whole setup can be emulated in Antmicro’s open source Renode framework, with multiple sensor nodes inside Renode and the companion app outside - a suitable test is provided in a dedicated Robot test.

The Myra System-in-Package

In the second iteration of the Environment Sensor, the processing part was compressed into a SiP with a form factor of 11.4 x 11.4 x 2.9 mm, replacing the MCU, FRAM and USB to UART converter with a single chip.

The SiP packs the WLCSP (Wafer Level Chip Scale Package) versions of those components into a chip-like enclosure, providing a standardized footprint and protection against environmental conditions such as humidity, temperature, shock or electric discharge. The chiplets are placed on an HDI (high-density interconnect) board - a PCB type dedicated for high density layout, serving as a substrate and footprint pads for the SiP.

As seen above, the Myra SiP includes:

• STMicroelectronics STM32G491REI6 MCU
• Fujitsu MB85RS1MTPW-G-APEWE1
• FTDI FT231XQ USB to UART converter
• Onsemi NCP177AMX330TCG LDO
• ECS Inc. International ECS-1612MV-080-CN-TR 8MHz main oscillator
• ECS Inc. International ECS-.327-12.5-1210-TR 32.768kHz Real Time Clock oscillator.

The SiP is enclosed in a 64-pin LGA package which exposes the following interfaces:

• USB 2.0 interface
• 2 x I2C interface
• 1x SPI interface
• 3 GPIO pins

All IO interfaces operate at 3.3V voltage level. The Myra SiP accepts 5V power supply voltage.

An interactive render with stackup, and in-browser preview of the PCB design for the Myra SiP can be found at our Open Hardware Portal.

For operation, the SiP requires just a USB connector and the SHT45 and BME280 sensing chips which could not be placed inside the SiP, as unlike the rest of the circuitry, they need to be exposed to external conditions. The SiP is a 64-pin LGA component and can be soldered directly onto a baseboard. For the purpose of bring-up and testing of the SiP, we created a development kit which is basically the Environmental Sensor but with the redundant components removed and - as a result - much simpler layout. The SiP baseboard is equipped with a USB-C connector for power and data transmission, as well as two QWIIC connectors, located at the sensor island and mainland.

The Myra SiP is also an example of a component that is included in or easy to use with most of the notable technologies Antmicro develops and uses, including our Renode framework, Hardware Component Database, Protoplaster, System Designer, Zephyr RTOS etc.

Below, you can see an interactive block diagram of the baseboard with the Myra SiP, prepared in Antmicro’s System Designer:

Miniaturized, reusable and secure hardware design with Antmicro

On top of significant miniaturization capabilities, SiP-based solutions offer better security and environmental protection compared to their functional counterparts with discrete components soldered on a PCB.

Antmicro can help you bring the benefits of SiPs to your project, enabling you to create miniaturized, secure and tailored solutions that can be brought to market faster and more reliably, using our open source-driven, transparent hardware development process. If you would like to learn more about our engineering services or are interested in building your next device with Antmicro, don’t hesitate to contact us at contact@antmicro.com.