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How can you verify microcontroller firmware updates?

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Microcontrollers are widely used in electrical design projects, from sensors and actuators to communication and control systems. They often need firmware updates to fix bugs, improve performance, or add features. But how can you verify that the firmware update is authentic, secure, and compatible with your hardware and software? In this article, you will learn some basic methods and tools to verify microcontroller firmware updates.

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1 Firmware verification process

Firmware verification is the process of checking that the firmware update is valid and matches the expected source and destination. It usually involves three steps: authentication, integrity, and compatibility. Authentication ensures that the firmware update comes from a trusted source and is not tampered with by malicious actors. Integrity ensures that the firmware update is not corrupted or damaged during transmission or storage. Compatibility ensures that the firmware update is suitable for your microcontroller model and version, and does not cause any conflicts or errors with your hardware or software.

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2 Authentication methods

Authenticating firmware updates is an important consideration for security and complexity, and there are various methods to do so. Digital signatures are a cryptographic technique that uses a pair of keys – one public and one private – to sign and verify the update. Hashing is another option, where a unique value is derived from the update using a mathematical function. And encryption is a process of converting the update into a secret code that can only be decrypted by the microcontroller with a key. All of these methods ensure that the update is from the original source, has not been altered, and is protected from unauthorized access or interception.

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Aniket Kelkar

Electrical Engineer | Specializing in Embedded Systems & Controls |Actively Pursuing Full-Time Opportunities
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Apart from the public and private keys, a hardware setup to enable updates to the firmware increases the security profile in a big way. Especially in safety-critical scenarios a device updating itself at the wrong time can be disastrous for the system. Hence the update cycle should not be handled by the firmware alone in such conditions.

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3 Integrity methods

Ensuring the integrity of firmware updates requires various methods, depending on the size and type of update, as well as the communication channel used. Checksums involve adding or XORing the bytes or bits of the update and sending it with the update. Cyclic redundancy checks (CRCs) divide the firmware by a predefined polynomial and can detect more errors than a checksum. Error correction codes (ECCs), such as Hamming code or Reed-Solomon code, are added to the firmware and allow the microcontroller to detect and correct errors without requesting a retransmission. This ensures that any updates are not damaged or lost during transmission or storage.

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Ronald Hill

Senior Embedded Electrical Engineer
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For internal firmware updates, it is important to have an agreed upon source of truth, such as a Product Lifecycle Management (PLM) system that is signed off by all stakeholders in the process. The operator performing the update is trained where to look for a given firmware and applies the update. Most direct hardware flashing tools offer a checksum that can be verified against a known checksum stored with the firmware in the PLM system. If not using PLM, any repository that can be access-controlled can suffice.

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4 Compatibility methods

To ensure the compatibility of firmware updates, depending on the architecture and design of the microcontroller and the firmware, there are various methods available. Version checking is a simple approach that compares the version number of the update with the version number of the current firmware on the microcontroller. Additionally, hardware identification verifies that the firmware update is intended for a specific microcontroller model and configuration. Software testing is another method that checks that the firmware update does not cause any errors or conflicts with existing software on the microcontroller or connected devices. By using these methods, you can ensure that updates are not outdated, mismatched, or faulty, and can prevent unnecessary or harmful updates, damage or malfunction, and bugs or failures.

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5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Ronald Hill

Senior Embedded Electrical Engineer
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Any firmware that is used on the production line should be in pre-compiled form. Re-compiling each flash (such as in Arduino Studio) introduces a risk of inserting or deleting data accidentally that will likely not be caught until the device is returned (imagine if someone changed the value of PI from 3.14 to 43.14, neither your compiler nor linker will catch that).

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How can you verify microcontroller firmware updates?

1

2

3

4

5

1 Firmware verification process

2 Authentication methods

3 Integrity methods

4 Compatibility methods

5 Here’s what else to consider

Electrical Design

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How can you verify microcontroller firmware updates?

1

2

3

4

5

1 Firmware verification process

2 Authentication methods

3 Integrity methods

4 Compatibility methods

5 Here’s what else to consider

Electrical Design

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