Securing firmware updates for IoT devices is a challenging undertaking because of their limited hardware resources. Most of the existing solutions are based on centralized architectures that may expose a single point of failure. Blockchain technology is largely accepted as a secure, robust and distributed platform for a number of different applications. This paper proposes the use of a blockchain platform to facilitate firmware updates for IoT devices. The distributed nature of the framework helps secure the firmware update process against single points of failure. In addition, the use of smart contracts can further strengthen the process by specifying firmware update conditions, verifying firmware update legitimacy, and protecting against potential cyber-attacks. Previous work in this area is extended by introducing a grammar and compiler to assist stakeholders in generating smart contracts. To validate the approach, a web- based prototype has been implemented to directly generate smart contracts in chaincode format that can be deployed in Hyperledger Fabric, an open source and permission-based blockchain framework. The grammar and compiler were evaluated for different use cases of the firmware update operations. Preliminary results with a prototype implementation show potential in simplifying the smart contract development process and reducing the amount of work needed to generate a working chaincode.