SX15007QB SEMTECH [Semtech Corporation], SX15007QB Datasheet - Page 16

• Manufacturer Part Number: SX15007QB
• Manufacturer: SEMTECH [Semtech Corporation]

ADVANCED COMMUNICATIONS & SENSING
Following procedure should be implemented on the host controller for a 4x4 keypad:
1. Set RegDir to 0xF0 (IO[3-0] as outputs, IO[7-4] as inputs) , set RegOpenDrain to 0x0F (IO[3-0] as open-drain
outputs), set RegPullup to 0xF0 (pull-ups enabled on inputs IO[7-4]).
2. Enable and configure debouncing on IO[7-4] (RegDebounceEnable = 0xF0, Ex : RegDebounceConfig = 0x05)
3. Enable and configure keypad scanning engine (Ex : RegKeyConfig = 0x7D) This will start an infinite loop with
the following sequence to IO[3:0]: ZZZ0, ZZ0Z, Z0ZZ, 0ZZZ. Make sure that scan interval is set to higher value
than the debounce time.
4. When a key is pressed, NINT goes low, key scan is halted and the key coordinates are stored in RegKeyData:
5. Restart from point 4.
This implementation allows the host to handle both single and multi-touches easily (fast AAAAAA sequence is a
long press of key A, fast ABABABAB sequence is key A and key B pressed together, etc)
4.6.3
Because of their 5.5V tolerant I/O banks with independent supply voltages between 1.2V and 3.6V, the
SX1508QB and SX1509QB can perform level shifting of signals from one I/O bank to another without uC
activity by programming the corresponding configuration register bits accordingly in RegLevelShifter (and
RegDir).
This can save significant BOM cost in a final application where only a few signals need to be level-shifted (no
need for an additional external level shifter IC).
Rev 3 – 9
Level Shifter
th
Sept. 2010
The column data will be stored in RegKeyData[7:4] (Note: column indication is active low)
The row data will be stored in RegKeyData[3:0] (Note: row indication is active low)
When RegKeyData is read, this data along with the interrupt is automatically cleared (same behavior
as reading RegData) and the key scan continues to the next row.
Figure 12 – 4x4 Keypad Connection to SX1508QB
- IO[3-0] as outputs (scanning)
- IO[7-4] as inputs
SX1508QB
Figure 13 – Level Shifting Example
SX1508/9QB
IO3
IO2
IO1
IO0
IO4
IO5
IO6
IO7
VCC1
VCC2
IO4
IO0
Y
RegKeyData =
1.2-3.6V
1.2-3.6V
16
X
tLevelShiftMin
SX1507QB/SX1508QB/SX1509QB
Y
World’s Lowest Voltage Level Shifting GPIO
1.2-5.5V
1.2-3.6V
X
with LED Driver and Keypad Engine
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