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  • UhClem's Avatar
    04-16-2019, 11:20 PM
    You are doing it differently. I have a group of buffers. When one gets full, data goes into the next one. The main loop watches for a buffer to be full. When that happens, it writes the data to the SD card and marks the...
    16 replies | 218 view(s)
  • UhClem's Avatar
    04-16-2019, 05:52 PM
    It is about speed. Ideally interrupt service should be fast so that it doesn't hold up the rest of the code. As for calling other functions, the only problem I have noticed is the C compiler getting stupid about saving...
    16 replies | 218 view(s)
  • UhClem's Avatar
    04-16-2019, 05:33 PM
    Yes. Writes to SD cards do that. Made worse by using a FAT file system. Allocating a new cluster triggers a scan of the FAT (1 or more reads) and update. Which takes time. Dependent on the state of the file system.
    16 replies | 218 view(s)
  • UhClem's Avatar
    03-15-2019, 12:22 AM
    By writing to a lot of different files you bring the dynamics of that into play. FAT file systems have just so many entries in the initial directory table and will have to allocate more space after some number of files....
    5 replies | 157 view(s)
  • UhClem's Avatar
    03-08-2019, 06:46 PM
    I have to wonder why you are using an SPI interface to the SD card when there is a dedicated SDHC high speed interface available.
    47 replies | 8297 view(s)
  • UhClem's Avatar
    02-26-2019, 04:47 PM
    According to the MPU9250 block diagram the I2C connection to the internal slave should be visible from the MPU9250 aux I2C pins. Monitoring that might give you some insight into where the problem starts.
    33 replies | 1506 view(s)
  • UhClem's Avatar
    02-26-2019, 04:36 PM
    I think you have an unrealistic expectation for low pass filter performance. If you set the corner frequency to 200Hz and use a 400Hz sample rate then the attenuation will never be better than 3dB at the Nyquist...
    5 replies | 190 view(s)
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SD, SPI and Interrupts 04-16-2019 11:20 PM
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