Low-power embedded system for acquisition and transmission of piezoresistive sensor measurements

• Autor(a) principal: Dias, Mário Gabriel Rodrigues da Rocha
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/41031
• topic: Firmware; Microcontrollers; FSR; Piezoresistive Sensors; Low-power; Low-power Communications; Wi-Fi Communications; Industrial Communications

In retail, a business inventory is one of its most valuable assets. Being able to track the available stock and potentially predict a stock shortage in the near future is a crucial feature in a business. To address this need, Exatronic developed an automated data acquisition system that identifies the product type based on its weight and area using a piezoresistive sensor on the shelf surface. However, a retail store may contain many shelves, and the power supplies may not be available, raising the need to battery supply these modules. This implementation demands efficient management of the energy available, allowing the module to run for a longer time without recharging. Therefore, reducing power consumption is a crucial point to make it possible. This dissertation describes the analysis of an existing prototype regarding how it is implemented and its power consumption, thus identifying possible improvements. After this identification, the development and the implementation of the new solution are presented, with the main objective of minimizing power consumption without compromising its main functionalities. This solution has a connection to an RS-485 bus to receive the reading requests and replies with the sensors’ values, and also an analog interface to communicate with the piezoresistive sensor. In addition, it has a temperature and humidity sensor to perform temperature compensation, since some of the shelves may be refrigerated. Keeping in mind that this prototype may be transformed into a marketable product, this solution assures a commitment between the components costs and their characteristics. For that purpose, the crucial parameters for each component were identified, and the components that meet these parameters and stayed within a price range were chosen. This dissertation details the architecture defined for this solution and the logical structure of the firmware. A set of tests were defined to assess the solution behavior. Firstly, the tests were applied to each function separately to ensure that every one was working. Finally, tests were made on the device as a whole to validate that its behavior corresponded to the requirements.