December
2004, Issue 173
Light-to-Frequency
Conversion (Part 1)
TSL230R-Based
Pulse Oximeter
SAMPLING
Next
month, I’ll describe the process of choosing the appropriate
mode and making sense out of the samples. In the meantime,
study Figure 5, which shows some TSL230R samples. I
used the on-board UART to dump each sample in a five-digit
decimal number (followed by a CR). I imported these
into Excel and used the graphing function to show you
what’s going on. I’ll use this to determine how to manipulate
the data into an indication of beats per minute.
|
(Click
here to enlarge)
|
Figure
5—This Excel chart displays imported sample values
over time. Samples of the output frequency (30 samples
per second formatted in microseconds) were sent
out the serial port and captured to a file by HyperTerminal. |
