Tool/software: Linux
We have a modem connected to Sitara AM437x using SPI and GPIO lines. The modem uses the processor's GPIO input to indicate (on falling edge) that data is received. The processor then reads the modem's status and data registers through the SPI interface. The data rate is around a byte every 8 milliseconds.
Our application (written in C) polls on the GPIO input that informs us of data availability every 8 millisecond. However, the GPIO read (using both memmap and also the sys/class interface) sometimes takes more than that thereby resulting in overflow conditions (where we miss a read of a data byte).
For cases where we toggle an output GPIO pins in short interval (for example every 15 milliseconds) from an application, we have noticed challenges to keep up with the time (like in a realtime system). We have tried both memmap and sys interface to access and toggle the GPIO pins.
Therefore, we have started to suspect an higher priority process/kernel module is preempting our application for long periods of time intermittently (sometimes we have noticed delays as long as 80 milliseconds) between togging the output GPIO (which we try to do every 15 milliseconds from the application).
We are using the Arago project's TI SDK 5.2.0.10 build for u-boot, kernel and root file system on which we are running our application.
