Starnote Carrier Board Design Guide
Starnote is the Blues satellite companion device. Like Notecard, it uses a standard M.2 Key E connector and can be embedded into a custom carrier board. Starnote is offered as Starnote for Skylo and Starnote for Iridium, which use the same M.2 Key E form factor.
This guide covers the Starnote-specific considerations involved in designing a custom carrier board: mounting, power, and the satellite antenna. Because every Starnote design also includes a Notecard, it should be read alongside the Notecard Carrier Board Design Guide.
noteStarnote is always paired with a Notecard
Starnote is not a standalone device. It works alongside a Notecard (e.g. Notecard Cellular, Notecard Cell+WiFi, or Notecard WiFi), adding satellite as an available radio access technology. The host communicates with Notecard, and Notecard in turn communicates with Starnote over UART.
As a result, a Starnote-capable carrier must accommodate both devices. For the Notecard side of your design (e.g. host serial interfaces, power, SIM, GPS, AUX pins, DFU, and more) follow the Notecard Carrier Board Design Guide. Note that Notecard for Skylo is a Notecard for the purposes of these guides, and is covered in that guide.
noteBlues always recommends starting from an existing Notecarrier design!
All Notecarrier design files are open source and available in the note-hardware GitHub repository. These Notecarriers all adhere to the concepts described below, and starting from one is the fastest, most reliable path to a working custom carrier board. We suggest Notecarrier XS for Starnote for Skylo and Notecarrier XI for Starnote for Iridium.
Table of Contents
Required Items
The following items are required for any host product that embeds a Blues Starnote.
M.2 Connector and Mounting
Starnote plugs into a standard M.2 Key E connector such as Amphenol MDT420E01001 (the same connector used by Notecard), and is secured along the opposite edge to a grounded standoff by a mounting screw. Blues reference designs use a Würth Elektronik 9774025151R paired with an M2.5x4 metric machine screw.
Because Starnote is larger than Notecard and its mounting-hole position differs (both from Notecard and between Starnote for Skylo and Starnote for Iridium), the standoff must be placed to match the specific device the carrier is designed for. See Footprint and Mounting for more information.
Notecard-to-Starnote Link
Because a Starnote-capable carrier must accommodate both devices, plan for two M.2 Key E connectors: one for Notecard and one for Starnote, linked over UART.
- Starnote for Skylo can alternatively connect to a Notecard through its 6-pin JST connector and a connector cable instead of a second M.2 connector.
- Starnote for Iridium connects to a Notecard over its M.2 connector exclusively.
Because the Notecard-to-Starnote link uses UART, the I2C interface can be left available as the host's interface to Notecard. For that reason we recommend routing both the UART and I2C interfaces on the Notecard side of your carrier; see Serial Notecard Request Interfaces in the Notecard Carrier Board Design Guide.
Power
Starnote is designed to be powered continuously and should be left powered at
all times. Provide constant power to VIO_P and VMODEM_P, and avoid
power-cycling or resetting the device after boot. See the
Low-Power Hardware Design
application note for more on power architecture.
warningFor Starnote, a power-loss event (i.e. losing power on VMODEM_P or VIO_P, or
pulling the RST pin low) risks rendering the satellite modem permanently
unusable. It is the designer's responsibility to ensure that Starnote-based
designs provide constant power to VMODEM_P and VIO_P.
VMODEM
VMODEM_P powers the device's radio and must be applied to pins 70, 72, and 74
of the M.2 connector. The required voltage and current depend on the product:
- Starnote for Skylo: 2.5VDC to 5.5VDC, capable of sustaining 350mA or more.
Size the
VMODEM_PandGNDtraces to handle this sustained current. - Starnote for Iridium: 3.5VDC to 4.5VDC. (Final current figures are still pending.)
warningStarnote for Iridium requires a VMODEM_P supply of 3.5VDC to 4.5VDC, a narrower
window than Notecard and Starnote for Skylo. A supply tuned for those devices (for
example, a 2.5V or 5.0V source) falls outside Starnote for Iridium's range, so
design the supply accordingly if your carrier must support it.
The satellite modem on Starnote for Iridium draws high current during transmit
bursts. The Notecarrier XI reference design accommodates this by feeding
VMODEM_P from a buck-boost supercapacitor charger/balancer, using
supercapacitors to supply those bursts and help maintain constant power to the
modem. Consider a similar approach in custom Starnote for Iridium carriers.
VIO
VIO_P powers the device's MCU and peripherals and must be applied to pins 2 and
4 of the M.2 connector. Supply either 1.8V or 3.3V:
- Starnote for Skylo: budget 150mA for Starnote.
- Starnote for Iridium: final figures are pending; as a planning estimate,
budget
VIO_Psimilarly to Starnote for Skylo (~150mA). Confirm against the Starnote for Iridium datasheet when its current requirements are published.
Ground
The 12 M.2 connector pins labeled as GND must be connected to the ground of the host system (pins 3, 5, 6, 11, 18, 33, 39, 45, 51, 57, 71, and 73).
Satellite Antenna(s)
Starnote connects to the satellite network through a U.FL antenna connection, and the host system must provide an appropriate antenna. Requirements differ by product:
- Starnote for Skylo (u.FL variant) provides two U.FL connectors, one for the
satellite radio (labeled
SAT) and one for GPS/GNSS, and operates on S-band and L-band (bands B23, B255, and B256). - Starnote for Skylo (Ignion variant) integrates both antennas on-board, so no external antenna connection is required.
- Starnote for Iridium provides a single U.FL connector for an Iridium-certified L-band antenna that also serves GPS/GNSS.
Satellite antennas require a clear, unobstructed view of the sky and are intended for outdoor placement. Be sure to observe a 5mm keep-out area around all antennas in all directions, avoiding ground planes, metal screws, metal components, and metal enclosures to avoid RF interference. Please see the Antenna Guide application note and the Starnote datasheet antenna requirements for Skylo and Iridium for additional information.
Recommended Items
Footprint and Mounting
Starnote follows the same swappable philosophy as Notecard but is physically larger, and its mounting-hole position differs by product. Plan for the largest footprint and the correct standoff location for the device(s) you intend to support:
- Starnote for Skylo: 30mm x 42mm (u.FL variant), or 30mm x 60mm for the Ignion variant, which integrates its antennas.
- Starnote for Iridium: 42mm x 42mm (wider than any Notecard) and 16g, which also warrants attention to mechanical mounting.
Because the standoff and mounting-hole positions differ between Notecards, Starnote for Skylo, and Starnote for Iridium, each Starnote is validated only against its matching Notecarrier (e.g. Notecarrier XS for Skylo and Notecarrier XI for Iridium).
Designing in the Notecard
Every Starnote design also includes a Notecard, and the host communicates with Starnote through that Notecard. For the rest of your carrier design (the host serial request interfaces, Notecard power, external SIM, cellular antenna(s), outboard DFU, GPS antenna, and the AUX, reset, and enable pins), follow the Notecard Carrier Board Design Guide.
