Gert Jan Schoneveld
Fork without short circuits
No extra hardware is needed besides the wires and switches. The columns are outputs configured with open drain. The rows are inputs configured with pull up resistors. A key press pulls down its row. With scanning the column is determined thereafter.
See SaveKeypad for an example usage.
Diff: keypad.cpp
- Revision:
- 0:2df66331c109
- Child:
- 10:9a9ec143840b
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/keypad.cpp Mon Jan 30 09:41:47 2012 +0000
@@ -0,0 +1,67 @@
+#include "keypad.h"
+
+Keypad::Keypad(PinName row3, PinName row2, PinName row1, PinName row0,
+ PinName col3, PinName col2, PinName col1, PinName col0,
+ int debounce_ms):
+ _row0(row0), _row1(row1), _row2(row2), _row3(row3),
+ _cols(col0, col1, col2, col3) {
+ _debounce = debounce_ms;
+ _setupRiseTrigger();
+}
+
+void Keypad::Start(void) {
+ _cols = 0x0F;
+}
+
+void Keypad::Stop(void) {
+ _cols = 0x00;
+}
+
+void Keypad::CallAfterInput(uint32_t (*fptr)(uint32_t index)) {
+ _input.attach(fptr);
+}
+
+void Keypad::_callback(int row, InterruptIn &therow) {
+ wait_ms(_debounce);
+ if (therow != 1)
+ return;
+
+ int c = -1;
+ _cols = _cols & 0x0E;
+ if (therow == 0)
+ c = 0;
+ else {
+ _cols = _cols & 0x0D;
+ if (therow == 0)
+ c = 1;
+ else {
+ _cols = _cols & 0x0B;
+ if (therow == 0)
+ c = 2;
+ else
+ c = 3;
+ }
+ }
+ _input.call(row * 4 + c);
+ Start(); // Re-energize all columns
+}
+
+void Keypad::_cbRow0Rise(void) {
+ _callback(0, _row0);
+}
+void Keypad::_cbRow1Rise(void) {
+ _callback(1, _row1);
+}
+void Keypad::_cbRow2Rise(void) {
+ _callback(2, _row2);
+}
+void Keypad::_cbRow3Rise(void) {
+ _callback(3, _row3);
+}
+
+void Keypad::_setupRiseTrigger(void) {
+ _row0.rise(this, &Keypad::_cbRow0Rise);
+ _row1.rise(this, &Keypad::_cbRow1Rise);
+ _row2.rise(this, &Keypad::_cbRow2Rise);
+ _row3.rise(this, &Keypad::_cbRow3Rise);
+}
\ No newline at end of file