Connecting an STN2120 to a custom slave PCB for OBD-II data acquisition presents challenges in achieving the desired refresh rate for real-time data analysis. Using a master PCB with an ATMEGA2560 to request and receive data from the STN2120 via UART may result in refresh rates exceeding one second per sensor, significantly slower than the CAN bus speed of up to 500 kbps. This article explores solutions for obtaining faster refresh rates when monitoring multiple sensor data points on the CAN bus.
The inherent latency of requesting and receiving data through the UART communication between the STN2120 and the ATMEGA2560 MCU limits the system’s ability to keep pace with the rapid data flow of the CAN bus. Requesting data for each of the 15 sensors individually introduces significant overhead, contributing to the slow refresh rate. While the STN2120 efficiently interprets CAN protocols, relying on the master MCU to actively poll for data creates a bottleneck.
To improve the refresh rate, consider implementing a data-driven approach instead of a request-response model. The STN2120 should be programmed to continuously transmit relevant sensor data over the UART connection to the master MCU without waiting for specific requests. This eliminates the delays associated with individual data requests. Optimizing the UART communication parameters, such as baud rate and data packet size, can further enhance data transfer speed.
Exploring the capabilities of the ATMEGA2560 MCU and available libraries is crucial. Certain libraries might enable the ATMEGA2560 to directly interpret CAN data, eliminating the need for the STN2120 as an intermediary. This direct interface with the CAN bus could significantly reduce latency and increase the refresh rate. However, implementing this requires careful consideration of the ATMEGA2560’s processing power and memory limitations.
Another potential solution involves using a more powerful microcontroller on the master board capable of handling higher data throughput and faster processing. This would allow for more efficient handling of the continuous data stream from the CAN bus. Alternatively, implementing a dedicated CAN controller on the master board in conjunction with the ATMEGA2560 could offload the CAN processing tasks and free up the MCU for data analysis and output control.
Ultimately, achieving a faster refresh rate for OBDII scanner live data from the speed sensor requires optimizing the communication protocol, potentially bypassing the request-response model, and exploring alternative hardware solutions like direct CAN interface or a more powerful microcontroller.
