Frequently Asked Questions

You've got questions? We've got answers. If you can't find them here, please reach out on the Blues Community Forum.

Blues Hardware

How is low-power mode implemented on Notecard?

When idle, meaning that the radio module on Notecard has been powered off and is not transmitting, Notecard uses a system power mode on the STM32L4 to enter STOP2 mode. In this mode, Notecard idles at ~8-18µA@5V depending on the specific Notecard model.

What are the minimum and maximum temperature and humidity levels for Notecard's optimal operation?

As per the Notecard datasheet, Notecard is meant to operate in the range of -35 C to 80 C. There are no specifications around humidity, but if ambient humidity is a concern, Notecard can be conformal coated at customer request prior to delivery. Please contact us for more information.

What is the expected bandwidth/throughput of Notecard Cellular?

Network bandwidth and throughput is largely dependent on RAT (e.g. NB-IoT, GSM, Cat-M, Cat-1, Cat-1 bis), device signal strength, and the state of Notecard's connection to Notehub. Therefore, Blues does not make any guarantees about expected bandwidth or throughput. That said, here are a few rules of thumb from the 3GPP around throughput for various RATs:

• LTE Cat-1 and Cat-1 bis: 10 MB down, 5MB up
• LTE-M: ~375KB down and 300KB up
• NB-IoT: ~60KB down and 30KB up

What are the expected latency thresholds for Notecard Cellular?

Because network latency is dependent on RAT (e.g. NB-IoT, GSM, Cat-M, Cat-1, Cat-1 bis), device signal strength, and the state of Notecard's connection to Notehub, Blues does not estimate nor document expected latency thresholds for the Notecard.

Does the Notecard store data locally, or is it transmitted to the cloud immediately?

Notecard is built around a durable, on-device queue. When your host adds a Note with a note.add request, it is saved to local flash first and synchronized to Notehub later, on a schedule defined by your hub.set configuration. This store-and-forward model means devices keep collecting data through connectivity gaps, and the host MCU never has to manage retries or buffering itself.

That said, Notecard can also push data on demand when your application requires it:

• Set "sync":true on a note.add request to trigger an immediate sync after the Note is queued.
• Set "live":true and "sync":true on a note.add request to bypass local flash entirely and send the Note in real time.
• Call hub.sync to manually flush any queued Notes.

These options are useful for low-latency events like alerts or commands that can't wait for the next scheduled sync.

Notecard provides approximately 1MB of user-accessible flash storage for queued Notes. The exact number of Notes that fit depends on Note size and whether the Notefile uses a Note Template. Non-templated Notefiles are capped at 100 unsynced Notes per file, while templated Notefiles store data far more compactly and can hold many more.

For the full mental model and recommended sync configurations, see Manage Connectivity and Sync Intentionally.

Connectivity

Cellular: How do I diagnose a Notecard that will not connect to a cellular network?

Please consult our guide on Diagnosing Cellular Connectivity Issues where we walk you through checking antenna placement, verifying your cellular signal strength, and troubleshooting low-quality or absent connections.

Cellular: Which LTE antennas do you recommend for fringe-area LTE-M or NB-IoT deployments?

1. General-Purpose: Use the flexible omni-directional LTE antennas provided by Blues (e.g. the single LTE antenna or dual LTE/GPS antenna). They both deliver reliable performance across all required LTE bands. The onboard Ignion antennas on Notecarrier A also cover most deployments without adding extra hardware.

2. Extended-Reach: Upgrade to a high-gain directional patch or yagi antenna tuned to your target LTE-M/NB-IoT bands, based on your region. Aim the antenna toward the nearest cell tower for maximum efficiency.

3. Custom: Work with Ignion (a Blues Partner) on a ground-plane-optimized, band-specific design.

Regardless of the antenna in use, the card.wireless API is useful for viewing the cellular signal strength from the device's most recent session.

Cellular: Why does my device have _health.qo events in Notehub with brown-out & hard reset messages?

Cellular modems draw significantly more current during transmission than at idle. If your power supply cannot sustain that peak draw, the voltage briefly drops below the Notecard's operating threshold — a brown-out — which triggers an automatic reset.

To resolve this, ensure your power supply can meet the Notecard's peak current requirements during modem transmit. See the Power Information section of your Notecard's datasheet for specifications. Also avoid power-cycling the Notecard to save power — its idle draw is already very low, and the startup cost of re-registering with the network after each reset far outweighs any savings.

Cellular: What happens when a Notecard's 500MB of included data runs out?

When an individual Notecard's remaining data drops below 100MB, Connectivity Assurance automatically adds another 500MB to that device. You can determine a Notecard's remaining data via the device's Data Plan tab in the Notehub UI, or via the Get Device Notehub API request.

Satellite: My Starnote for Skylo is unable to connect to any satellites. What is the correct procedure for aligning my antenna?

Regardless of whether you are using a Starnote for Skylo with onboard antennas or the Skylo-certified external flexible antenna provided by Blues, your antenna needs a clear, unobstructed, view of the sky. Be sure to orient your antenna's "flat" face (whether it's onboard or external) toward the sky. Ensure no trees, buildings, or heavy cloud cover block the antenna's view of the sky. Even thin foliage can degrade a signal from GEO satellites.

WiFi: What should I do when Notecard WiFi is unable to connect to a WiFi access point?

1. Verify that your WiFi access point supports the 2.4 GHz band required by Notecard WiFi. Depending on the router, the access point may broadcast a separate 2.4 GHz SSID, or the router may automatically assign the device to the correct band automatically.

2. Double check that you've entered the correct SSID and case-sensitive password when using the card.wifi API.

3. On the router itself, make sure there is no MAC-filtering that could be blocking new devices from joining the network.

LoRa: How do I restore network connectivity after performing a factory reset on my Blues Indoor LoRaWAN Gateway?

If you ever perform a full factory reset on your Blues gateway, please reach out on the Blues Community Forum to notify a Blues staff member. There are additional reset procedures that Blues staff must perform to get your gateway back online.

LoRa: How do I connect my Notecard for LoRa devices to a public LoRaWAN server?

Notecard for LoRa will automatically work with any LoRaWAN gateway on The Things Stack (including public LoRaWAN gateways). However, if you are connected to a LoRaWAN gateway on The Things Stack and Notecard for LoRa is not working, please verify that Packet Broker is enabled on the gateway, as detailed in Connecting to a non-Blues Gateway.

Notehub

How long does Notehub store my events?

Notehub retains events for 7 days on the Essentials plan. Enterprise plans offer extended retention periods. See Blues Pricing for details.

During the retention window, you can view events in Notehub and query them via the Notehub API. After 7 days, events are no longer available in Notehub. This means you need alternative storage if you require data retention beyond this window, which most production applications do.

Remote DFU

What other architectures does Blues support for remote Device Firmware Updates (DFU) with Notecard Outboard Firmware Update on the Host MCU?

Notecard Outboard Firmware Update is currently supported on all STM32 boards with ROM bootloader support, ESP32, as well as any target that implements the MCUboot bootloader, including nRF52840 devices. For architectures where outboard DFU is not supported, DFU is still possible, but the capability needs to be included in the host MCU firmware to migrate the host MCU firmware from the Notecard to the host MCU.

How does the Binpack utility encrypt the binary for the remote host when using Notecard Outboard Firmware Update, and at what stage does decryption occur?

Binpack is a packaging utility for multi-part binary files, not an encryption approach. At its core, a .binpack file is a binary with a custom header that contains binary file names and memory addresses. When the Notecard reads this header, it can determine the location in flash to lay down each binary in the bundle.

Security

Is secure boot functionality available on the Notecard?

No. There are no cryptographic secrets in the Notecard firmware nor anywhere in the Notecard flash memory. We rely upon a secure element with embedded keys/certificates for TLS network security. What's more, Notecard firmware can only be loaded from Notehub.io on a TLS session; the firmware will not load arbitrary binary images. Stated differently, the firmware will never update or replace itself with an image that is not generated by Blues Inc. and delivered over a TLS session. This guarantee is chained to the TLS authentication and thus the certificate in the secure element. However, as with any embedded device, if an attacker gained physical access to a Notecard they could sideload custom firmware on the device.

How does the .qos extension of a Notefile facilitate data encryption?

Notefile names that terminate in "s" are sent to Notehub over a TLS connection, but the files themselves are not encrypted. The data itself can also be encrypted using end-to-end encryption approaches supported by the Notecard.

What types of passwords, tokens, or other sensitive information could be exposed if an attacker gains physical access to a Notecard device?

None. The Notecard stores its keys in a secure enclave (STSAFE Secure Element). These keys are not stored in RAM or Flash and no other passwords, tokens, or other sensitive information is stored on or transmitted by the Notecard. Please note that the Notecard does transmit whatever arbitrary data is provided to it by a host, so it is also up to the application developer to ensure that sensitive information specific to a user application stays out of firmware and is not passed to the Notecard, unless that data is encrypted using an end-to-end encryption approach.

Pricing

Do I have to pay to use Notehub?

Blues Notehub does not use monthly subscription fees. Instead, when using Notehub you pay for two things: events and data usage.

Event pricing is based on the number of event credits your billing account uses each month. On Essentials plans, your billing account is "topped up" to 5,000 free event credits each month, and usage beyond that is billed according to the rates listed on blues.com/pricing. Enterprise plans use volume pricing as defined in your agreement.

Data usage comes from the connectivity your devices use (cellular or satellite). All Blues cellular and satellite devices include bundled data, with additional usage handled automatically once that data is depleted.

• Cellular: When a Notecard reaches 100MB of remaining data, Notehub's Connectivity Assurance adds 500MB of data to the device's data plan. This data is valid for up to 10 years. Each additional 500MB of data costs $10 for North America Notecards (e.g. NBNA, MBNA, WBNA) and $15 for international Notecards (e.g. NBGL, MBGL, WBGL, WBEX). See Managing Connectivity Assurance.

• Satellite: When a Starnote's bundled data is depleted, you are charged $0.75/KB for all additional usage. See How Satellite Data is Billed.

How does the payment structure work when using an external SIM with the Notecard?

When using an external SIM with Notecard, you need to acquire and pay for provider data and access separate from Blues. Data and coverage is only bundled with the internal Notecard SIM only. On the Notehub side, event usage is metered the same regardless of which SIM type is used.

How is satellite data billed?

All Blues satellite products (Notecard for Skylo, Starnote for Skylo, and Starnote for Iridium) include a fixed lifetime data allocation for both inbound and outbound traffic. Once this allocation is exhausted, the device continues to operate normally, and any additional usage is billed monthly in arrears to the credit card on the project’s billing account.

Data usage is calculated based on packet size, which varies by satellite network:

• When using Iridium, satellite packets have a minimum billable size of 10 bytes and a maximum supported size of 340 bytes. Packets smaller than 10 bytes are billed as 10 bytes.

• When using Skylo, satellite packets have a minimum billable size of 50 bytes and a maximum supported size of 256 bytes. Packets smaller than 50 bytes are billed as 50 bytes.