at42qt1481 ATMEL Corporation, at42qt1481 Datasheet - Page 51

• Manufacturer Part Number: at42qt1481
• Description: 48-key Qmatrix Ic
• Manufacturer: ATMEL Corporation

5.23
5.24
5.25
9621B–AT42–06/11
Frequency Hopping Mode – FHM
Frequency 0 – FREQ0
Frequency1 – FREQ1
If frequency hopping is enabled, the QT1481 continually monitors the noise across all keys and
switches frequency to try and find the frequency with least signal noise. If frequency hopping is
disabled, the QT1481 always uses the same frequency, defined by FREQ0.
This function is programmed on a global basis. See
FHM Default value:
FHM Possible range:
Up to three different operating frequencies may be configured, using FREQ0, FREQ1 and
FREQ2. These functions define the idle time between pulses in the burst. Larger values of
FREQ0 yield longer time between pulses and thus a lower fundamental frequency.
If frequency hopping is enabled, the QT1481 can hop between these three frequencies. If it is
desired to configure two different frequencies only, two of the frequencies should be configured
to the same setting. If frequency hopping is disabled, the QT1481 always uses the same
frequency, defined by FREQ0. Frequency hopping might not be desirable in all applications and
it might be more appropriate to preselect a burst frequency at the factory which is known not to
coincide with other operating frequencies within the end product or other frequencies in the
operating environment. In such cases, FHM can be set at zero, and the burst frequency set with
FREQ0.
Together with DWELL, FREQ0 allows the fundamental frequency to be set in the range
31 kHz – 943 kHz. The frequency for a specific DWELL and FREQ0 combination should be
measured using an oscilloscope (temporarily disable frequency hopping to make the
measurement easier).
This function is programmed on a global basis. See
FREQ0 Default value:
FREQ0 Possible range:
Up to three different operating frequencies may be configured, using FREQ0, FREQ1 and
FREQ2. These functions define the idle time between pulses in the burst. Larger values of
FREQ1 yield longer time between pulses and thus a lower fundamental frequency.
Together with DWELL, FREQ1 allows the fundamental frequency to be set in the range
31 kHz – 943 kHz. The frequency for a specific DWELL and FREQ1 combination should be
measured using an oscilloscope (temporarily disable frequency hopping to make the
measurement easier).
This function is programmed on a global basis. See
FREQ1 Default value:
FREQ1 Possible range:
1 = Calibrate all keys after hop
0 – 2
24 (delay cycles)
0 – 63 (Highest frequency to Lowest frequency)
30 (delay cycles)
0 – 63 (Highest frequency to Lowest frequency)
(0 = off
1 = Calibrate all keys after hop
2 = Adjust each key's reference during hop)
Table 5-7 on page
Table 5-7 on page
Table 5-7 on page
57.
57.
57.
AT42QT1481
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