--- title: Frequently Asked Questions description: Frequently asked questions related to IoT connectivity with Blues, Notecard, and Notehub. source_url: https://dev.blues.io/support/frequently-asked-questions/ canonical_url: https://dev.blues.io/support/frequently-asked-questions/ markdown_url: https://dev.blues.io/support/frequently-asked-questions.md --- # 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](https://discuss.blues.com/). ## Blues Hardware ### Where can I buy Blues hardware? Blues hardware (Notecards, Notecarriers, starter kits, and accessories) is available directly from the [Blues Shop](https://shop.blues.com?utm_source=dev-blues\&utm_medium=web\&utm_campaign=store-link). This is the primary channel for purchasing individual units and small quantities. For larger orders or volume pricing, contact the Blues sales team at [blues.com/contact-sales/](https://blues.com/contact-sales/). ### 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](https://dev.blues.io/datasheets/notecard-datasheet.md), 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](https://blues.com/contact-sales/) for more information. ### What is the expected bandwidth/throughput of Notecard Cellular? Network bandwidth and throughput is largely dependent on [RAT](https://dev.blues.io/api-reference/glossary.md#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](https://dev.blues.io/api-reference/glossary.md#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. ### Why am I getting I2C errors with the Notecarrier Pi on a Raspberry Pi? Persistent I2C errors such as `[Errno 110] Connection timed out`, `Notecard not responding to newline`, or `Exception: Failed to reset Notecard.` are typically caused by the well-known I2C clock-stretching limitation on the Raspberry Pi's BCM SoCs. The recommended workaround is to switch to serial (UART) communication using the Notecarrier Pi's `SERIAL TXRX` DIP switch. See the [DIP Switches](https://dev.blues.io/datasheets/notecarrier-datasheet/notecarrier-pi-v2-0.md#dip-switches) section for details, and use [`notecard.OpenSerial`](https://dev.blues.io/tools-and-sdks/firmware-libraries/python-library.md#serial-configuration) in your Python code to open `/dev/serial0` at 9600 baud. ### 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](https://dev.blues.io/api-reference/notecard-api/note-requests/latest.md#note-add) request, it is saved to local flash first and synchronized to Notehub later, on a schedule defined by your [hub.set](https://dev.blues.io/api-reference/notecard-api/hub-requests/latest.md#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](https://dev.blues.io/api-reference/notecard-api/hub-requests/latest.md#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](https://dev.blues.io/notecard/notecard-walkthrough/low-bandwidth-design.md#working-with-note-templates). 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](https://dev.blues.io/guides-and-tutorials/best-practices-for-production-ready-projects.md#manage-connectivity-and-sync-intentionally). ### How large can a Note be? A [Note](https://dev.blues.io/api-reference/glossary.md#note)'s `body` is JSON that the Notecard queues locally and later syncs to Notehub. There is no small fixed cap enforced at the API, but as a practical rule of thumb keep any single `note.add` request—including the Note's `body`—at or below **8KB (8192 bytes)**. Staying under 8KB keeps each Note comfortably within the Notecard's internal sync and web-transaction buffers and ensures reliable delivery over cellular and WiFi. Binary data attached through a Note's `payload` field is limited separately, to 256 bytes, unless the Notefile uses a [Note Template](https://dev.blues.io/notecard/notecard-walkthrough/low-bandwidth-design.md#working-with-note-templates). On Notecard for LoRa, and when syncing over satellite (NTN), Notes are subject to much smaller, network-imposed size limits, so these Notes must use a [Note Template](https://dev.blues.io/notecard/notecard-walkthrough/low-bandwidth-design.md#working-with-note-templates) to keep each Note compact. ## 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](https://dev.blues.io/support/diagnosing-cellular-connectivity-issues.md) 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](https://shop.blues.com/collections/accessories/products/flexible-cellular-or-wi-fi-antenna?utm_source=dev-blues\&utm_medium=web\&utm_campaign=store-link) or [dual LTE/GPS antenna](https://shop.blues.com/collections/accessories/products/dual-flexible-antenna-cell-wi-fi?utm_source=dev-blues\&utm_medium=web\&utm_campaign=store-link)). They both deliver reliable performance across all required LTE bands. The onboard Ignion antennas on [Notecarrier A](https://dev.blues.io/datasheets/notecarrier-datasheet/notecarrier-a-v2-3.md) 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](https://ignion.io/) (a Blues Partner) on a ground-plane-optimized, band-specific design. Regardless of the antenna in use, the [card.wireless API](https://dev.blues.io/api-reference/notecard-api/card-requests/latest.md#card-wireless) 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](https://dev.blues.io/datasheets/notecard-datasheet.md) 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](https://dev.blues.io/notehub/notehub-walkthrough.md#managing-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](https://dev.blues.io/api-reference/notehub-api/device-api.md#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](https://dev.blues.io/api-reference/notecard-api/card-requests/latest.md#card-wifi). 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](https://discuss.blues.com/) 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](https://www.thethingsnetwork.org/map)). 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](https://dev.blues.io/lora/connecting-to-a-lorawan-gateway.md#connect-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](https://blues.com/pricing/) for details. During the retention window, you can view events in Notehub and query them via the [Notehub API](https://dev.blues.io/api-reference/notehub-api.md). 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. ### What is the difference between the Notehub Essentials and Enterprise plans? Both plans use the same Notehub platform. The main differences are in: - **Event credits.** On the Essentials plan, each billing account is topped up to **5,000 free event credits per month**, with usage beyond that billed at the rates published on [blues.com/pricing](https://blues.com/pricing). Enterprise plans use **volume pricing as defined in your agreement** instead. See [Do I have to pay to use Notehub?](#do-i-have-to-pay-to-use-notehub). - **Event retention.** Essentials retains events for **7 days**; Enterprise plans offer **extended retention periods**. For a full comparison refer to [Blues Pricing](https://blues.com/pricing/). ### Can I add a device to a Notehub project before it has connected? Yes. Use the [Provision Device API](https://dev.blues.io/api-reference/notehub-api/device-api.md#provision-device) or a [batch job](https://dev.blues.io/notehub/notehub-walkthrough.md#running-batch-jobs) to assign a device to a [ProductUID](https://dev.blues.io/api-reference/glossary.md#productuid) ahead of time, identifying the device by its [DeviceUID](https://dev.blues.io/api-reference/glossary.md#deviceuid) (printed on the Notecard). You can optionally preassign a serial number and one or more [fleet](https://dev.blues.io/api-reference/glossary.md#fleet) associations. The provisioned configuration is applied automatically the first time the device connects to your project, which makes it useful for zero-touch provisioning workflows where devices are configured before they are deployed. To read more on Notehub provisioning patterns, see [Out-of-the-Box Provisioning](https://dev.blues.io/guides-and-tutorials/fleet-admin-guide.md#out-of-the-box-provisioning) in our Fleet Admin Guide. ## 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](https://dev.blues.io/notehub/host-firmware-updates/notecard-outboard-firmware-update.md) 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](https://dev.blues.io/notehub/host-firmware-updates/notecard-outboard-firmware-update.md#wrapping-binaries-using-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](https://dev.blues.io/api-reference/glossary.md#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](https://dev.blues.io/guides-and-tutorials/notecard-guides/encrypting-and-decrypting-data-with-the-notecard.md) 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](https://dev.blues.io/notehub/notehub-walkthrough.md#understanding-event-credits) your [Organization](https://dev.blues.io/api-reference/glossary.md#organization) uses each month. On Essentials plans, your Organization 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](https://blues.com/pricing). Enterprise plans use volume pricing as defined in your agreement. > **Note:** > > Notehub does not charge for [platform events](https://dev.blues.io/api-reference/glossary.md#platform-event). 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](https://dev.blues.io/notehub/notehub-walkthrough.md#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-is-satellite-data-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. > **Note:** > > For other pricing questions, please consult the [pricing structure on blues.com](https://blues.com/pricing/). ### 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 10,000 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.