PICO USB TC-08 - Page 13

Technical reference
12
© 2005 Pico Technology Limited. All rights reserved.
USBTC08044-2
Note: The function call overhead can be significant, since it takes approximately 360 ms
to convert all 9 channels, equating to 40 ms per channel. To reduce this overhead,
disable channels that are not required.
Example
The following code is a fragment of a C application demonstrating how to use Get Single
mode with the USB TC-08 driver:
//========================================================
// Setting up and converting readings with Get Single mode
//========================================================
usb_tc08_set_mains
(handle,
0
);
// use 50Hz mains noise rejection
for
(channel =
0
; channel <
9
; channel++)
{
// set each channel up as a type K thermocouple
// channel 0 is the cold junction and will be enabled
// by setting the third argument to anything other than ' '
usb_tc08_set_channel
(handle, channel,
'K'
);
}
// find out the approximate conversion time
// for a call to usb_tc08_get_single
minimum_interval =
usb_tc08_get_minimum_interval_ms
(handle);
printf(
"Conversion time: %d\n"
, minimum_interval);
// Collect 10 readings over approximately 9 minutes
last_time = GetTickCount();
for
(i =
0
, i <
10
, i++)
{
// do the conversion for all channels
usb_tc08_get_single
( handle,
value_array,
// short value_array[9]
&overflow_flags,
0
);
// degrees Celsius units
// print out the values
printf(
"\n\nTime: %d minute(s)"
, i);
for
(c =
0
; c <
9
; c++)
{
// check for overflows on each channel
// with a bitwise & comparator
// shift the comparison bit to match the channel
if
(overflow_flags & (
1
<< c))
{
printf(
"\nChannel %d overflowed"
, c);
}
else
// no overflow
{
printf(
"\nChannel %d: %f"
, c, value_array[c]);
}
}
if
(i <
9
)
{
while
(
60000
>
(GetTickCount() - last_time))
// 60000ms = 1 minute
{
Sleep(
100
);
// let other applications run
}
last_time = GetTickCount();
}
}