# Conception of a System-on-Chip (SoC) Platform to Enable EMG-Guided Robotic Neurorehabilitation
## 3 System Requirements and Architecture Implementation  
When designing our system of acquisition and processing, several key requirements must be met to ensure its functionality, precision, and adaptability. The following outlines the primary characteristics necessary for achieving optimal performance in EMG-based systems. The primary requirements are as follows:  
* Four channels per muscle group: For accurate measurement of a muscle group, a minimum of four differential channels per group is required, with an additional reference channel. This setup allows for the reliable characterization of both contractions and relaxations of antagonistic muscles within the same group, ensuring precise movement analysis. * High acquisition frequency and resolution: To capture the majority of the EMG signal, the acquisition rate should be as close as possible to twice the upper limit of the signal's bandwidth, in accordance with the Nyquist-Shannon sampling theorem. Given that the upper bandwidth limit for an EMG signal is 10 kHz, the minimum acquisition frequency should be approximately 20 kHz or higher. Additionally, due to the low amplitude of the EMG signal, the acquisition system must include an amplification phase and a resolution of at least 16 bits to accurately capture signal details. * High processing capacity: To significantly reduce the bandwidth required for transmitting information outside the device, an integrated system with sufficient computational capacity to process the acquired signals is essential. This approach minimizes data transmission by sending only specific commands to the exoskeleton actuators, thereby enhancing efficiency. * Fast processing and flexibility: The device must be sufficiently flexible to allow for the programming and construction of the entire EMG signal processing architecture. It should be capable of handling near real-time processing to ensure that the resulting exoskeleton movements are reliable and fluid. * Portability: The acquisition system should be compact enough to be transported with one hand, facilitating its use in various contexts beyond the exoskeleton application. This portability feature enables convenient testing and measurement in diverse environments. The analog signal captured by the electrodes must be conditioned and digitized to facilitate its analysis and use. While final products often employ custom-designed circuits tailored to the specific application, the complexity of designing, calibrating, and managing communication in these circuits makes commercial acquisition AFEs (Analog Front-Ends) a practical choice for early development stages. Commercial AFEs, although more expensive and less application-specific, provide a reliable and rapid solution for prototyping. For this project, the ADS1298 [19], part of Texas Instruments(r) (headquartered in Dallas, TX, USA) ADS129x family, was selected due to its configurable multichannel architecture, low power consumption, and high performance in biomedical signal acquisition, such as EMG, ECG (Electrocardiography), and EEG (Electroencephalography). The ADS1298 integrated circuit offers eight channels, providing greater flexibility compared to other devices in the series. It also includes a respiration module which, although not used in this work, could be valuable for future developments. For the initial development phase, we utilized the Texas Instruments ADS1298 RECCFE development board as analog front end (AFE), which integrates the ADS1298R chip. This enabled us to refine and mature our design concept. Subsequently, using the same chip, we developed custom hardware, ensuring reliability and functionality after validating and testing the work conducted with the development board. The ADS1298 supports sampling rates of up to 32 kSPS, but at higher frequencies, the bit resolution decreases, as specified in the datasheet: 24 bits for up to 8 kSPS, 19 bits at 16 kSPS, and 17 bits at 32 kSPS. For this project, a sampling frequency of 8 kSPS was selected to ensure maximum resolution.