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Streaming

If a device is connected to a PICO USB parallel port, data is collected asynchronously, without any

intervention from the PC. This gives considerably more reliable data collection, and sampling does not

interfere with the operation of the your computer.

When collecting data from a streaming device using the drivers, three modes are available:

BM_SINGLE - collect a single block of data and exit

BM_WINDOW - collect a series of overlapping blocks of data

BM_STREAM - collect a continuous stream of data.

BM_SINGLE is useful when you wish to collect data at high speed for a relatively short period. For

example, to collect 1000 readings in 50ms.

BM_WINDOW is useful when collecting several blocks of data at relatively low speeds- for example when

collecting 10000 samples over 10 seconds. Collecting a sequence of SINGLE blocks like this would take

10 seconds for each block, so displayed data would not be updated frequently. Using windowing, it is

possible to ask for a new block more frequently, for example every second, and to receive a block

containing nine seconds of data that have already been seen and one second of new data. The block is

effectively a 10-second ‘window’ that advances one second each time.

BM_STREAM is useful when you need to collect data continuously for long periods. In principle, it would

be possible to collect data indefinitely. Each time adc100_get_values is called, it returns the new readings

since the last time it was called. No_of_values passed to adc100_run must be sufficient to ensure that the

buffer does not overflow between successive calls to adc100_get_values. For example, if you call

adc100_get_values every second, and you are collecting 500 samples per second, no_of_values must be

at least 500, and preferably 1000 to give some allowance for delays in the operating system.

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ADC 100 Specifiche Pagina 6