Frequently Asked Questions

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Blues Hardware

How is low-power mode implemented on the Notecard?

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

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

As per the Notecard datasheet, the 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, the Notecard can be conformal coated at customer request prior to delivery. Please contact us for more information.

What is the expected bandwidth/throughput of the cellular-based Notecards?

Network bandwidth and throughput is largely dependent on RAT (e.g. NB-IoT, GSM, Cat-M, Cat-1), device signal strength, and the state of the Notecard's connection to Notehub, so 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: 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 the cellular-based Notecards?

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

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

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

When using an external SIM with the Notecard, the customer will 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 SaaS side, consumption credit usage is metered the same regardless of which SIM type is used.