Solution: Data Storage Options and Data Logging

Data Storage Options

Storage	Nature	Typical use
SRAM	Volatile, fast	Temporary buffers
EEPROM	Non-volatile	Calibration/configuration data
Internal Flash	Non-volatile	Firmware and small datasets
External Flash	Non-volatile	Larger embedded storage
SD card	Removable, high capacity	Continuous data logging
USB/Computer	External	Long-term transfer/storage

Data Logging Process

Sensor → ADC → MCU → RAM Buffer → Storage Interface → File/Memory

Steps

1. Initialize the sensor and ADC.
2. Configure the sampling timer.
3. Acquire a sample at every sampling instant.
4. Convert the ADC code into the required format.
5. Add a timestamp or channel identifier when necessary.
6. Store samples in a RAM buffer.
7. When the buffer is sufficiently full, write a block to non-volatile storage.
8. Repeat until logging ends.

Why Buffering is Important

Storage devices such as SD cards may have variable write latency. A RAM buffer allows acquisition to continue while data is being written in blocks.

Example Pseudocode

while (logging)
{
    sample = read_adc();
    buffer[index++] = sample;

    if (index == BUFFER_SIZE)
    {
        storage_write(buffer, BUFFER_SIZE);
        index = 0;
    }
}

A real implementation should also handle write failures, buffer overflow, timestamps, file-system errors and safe shutdown.

Storage Selection

• Use EEPROM for small calibration/configuration data.
• Use Flash for firmware and moderate non-volatile data.
• Use SD cards for large continuous logs.
• Use computer/USB/network storage when very large datasets must be transferred or archived.

Conclusion

Efficient data logging depends on selecting suitable storage, using buffering and ensuring that the sustained storage throughput is greater than the incoming data rate.