at42qt1481 ATMEL Corporation, at42qt1481 Datasheet - Page 53

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

5.30
5.31
9621B–AT42–06/11
Setups CRC – SCRC
Setups Block
Note:
Command 0x02 can be invoked to automatically fill out the CFO_1 and CFO_2 values.
Alternatively, CFO_1 and CFO_2 can be manually configured.
Once FREQ0, FREQ1 and FREQ2 have been configured for the three chosen frequencies,
CFO_1 and CFO_2 should be loaded with the signal offsets appropriate for the signal shifts
observed when switching between the three different frequencies.
Follow these steps to determine the different signal levels for each key at each frequency and to
determine appropriate values to load into CFO_1 and CFO_2.
CFO_1/2 Default value: 0
CFO_1/2 Possible range: 0 – 255
The setups block terminates with a 16-bit CRC, SCRC, of the entire block. The formulae for
calculating this CRC is shown in
Setups data is sent from the host to the QT1481 in a block of hex data. The block can only be
loaded in Setups mode following two 0x01 commands
this datasheet pertains to has the same block length. Refer also to
further details.
1. Configure FHM = 0 to disable frequency hopping temporarily.
2. Configure FREQ0 to select the highest of the chosen frequencies. i.e. FREQ0 should
3. Recalibrate all keys.
4. Make a note of each key's reference level, Ref(k, f0)
5. Configure FREQ0 to select the second of the chosen frequencies.
6. Recalibrate all keys.
7. Make a note of each key's reference level, Ref(k, f1).
8. Configure FREQ0 to select the last of the chosen frequencies.
9. Recalibrate all keys.
10. Make a note of each key's reference level, Ref(k, f2).
11. Determine the difference in signal for each key in turn when the frequency changes
12. Store Diff(k, f0, f1) into the corresponding CFO_1 for the k.
13. Determine the difference in signal at each key when the frequency changes from
14. Store Diff(k, f0, f2) into the corresponding CFO_2 for key k.
15. Configure FHM = 2.
be set to a lower value than FREQ1 and FREQ2.
from FREQ0 to FREQ1, using the following equation:
FREQ0 to FREQ2, using the following equation:
(this value will nearly always be positive. If it is negative, set Diff(k, f0, f1) to zero)
(this value will nearly always be positive. If it is negative, set Diff(k, f0, f1) to zero)
Configure FREQ0, FREQ1 and FREQ2 before trying to configure CFO_1 and CFO_2.
Diff(k, f0, f1) = Ref(k, f0) - Ref(k, f1)
Diff(k, f0, f2) = Ref(k, f0) - Ref(k, f2)
Appendix
A. The low order byte should be sent first.
(Section 4.3 on page
Table 5-7 on page 57
AT42QT1481
27). The QT1481
for
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