Understandig analog signals in sigrok
There are tree main use cases for analog signals in sigrok:
- Fast sample data for scopes
- Input file formats: CSV, Feed Queue, Raw Analog, Saleae and WAV
- Slow sample data for measurement devices like multimeters, power supplies, sound level meters and so on.
A minor use case for analog signals is buffered measurement data for a small number of devices: One multimeter (mooshimeter-dmm), one thermometer (lascar-el-usb) and one (or two) sound level meters (cem-dt-885x and maybe kecheng-kc-330b).
All sample data for scopes is related to a sample rate, so the time stride between the individual sample points can be calculated. None of the scopes is announcing their actual sample rate (SR_CONF_SAMPLERATE) via a SR_DF_META packet, but only by a config key (get/set/list).
Most scopes use SR_FRAME for transmitting their buffer (display buffer, sample buffer or similar). Some scopes don't use frames and transmit a continuous stream of sample data (fxla, hantek-xxxx) (?) will this really be continuous
This input formats use SR_CONF_SAMPLERATE via a SR_DF_META packet to announce their sample rate: CSV, Raw Analog, Saleae and WAV. This input format doesn't announce a sample rate: Feed Queue.
Non of the input formats is using frames.
Measurement devices normally (exceptions see below) don't have a sample rate, but even when it doesn't matter for the SR_ANALOG packet for live data. The individual drivers only receive one sample at a time and forward the samples via SR_ANALOG one by one. A sample rate must not be used, because the time stride between each sample can vary depending on various facts, e.g. the connecting interface (USB, RS232, GPIB, etc.). (!) A timestamp is missing
When measurement devices transmit samples between a frame, this means that these sample points were received at the same time by the driver (reload pro).
This is a specific use case and rater unclear for me at the moment.
(?) Is the buffer send over and over when in acquisition mode (?) Is this data represented as a "normal" channel