One of my customer used STM32 to communicate with ADS1198. When he used sample rate 500sps to sample 500 points, the total time will be 1s in theory, but the total time is 4s. Then he increased the sampling rate to 1 KSPS, sampling 500 points of time is also close to 4s. The sampling rate has been increased to 4Ksps, and the time of sampling 500 points has been shortened to 2s. What is reason may cause this problem? Does there any erro on the program?