Support detaching & re-attaching the expander

Partly addresses #5. We still need to gracefully handle when the expander is not
coming back.

Signed-off-by: Gergely Nagy <algernon@keyboard.io>

src/kaleidoscope/hardware/ErgoDox.cpp

@@ -92,6 +92,8 @@ void ErgoDox::readMatrixRow(uint8_t row) {
 void ErgoDox::readMatrix() {
   do_scan_ = false;
 
+  scanner_.reattachExpanderOnError();
+
   for (uint8_t row = 0; row < ROWS / 2; row++) {
     scanner_.selectRow(row);
     scanner_.selectRow(row + ROWS / 2);

src/kaleidoscope/hardware/ErgoDoxScanner.cpp

@@ -45,11 +45,7 @@ namespace hardware {
 uint8_t ErgoDoxScanner::initExpander() {
   uint8_t status = 0x20;
 
-  if (i2c_initialized_ == false) {
+  i2c_init();
-    i2c_init();
-    i2c_initialized_ = true;
-    _delay_ms(1000);
-  }
 
   status = i2c_start(I2C_ADDR_WRITE);
   if (status)
@@ -187,5 +183,18 @@ out:
   }
 }
 
+void
+ErgoDoxScanner::reattachExpanderOnError() {
+  static uint8_t attach_counter;
+
+  if (!expander_error_)
+    return;
+
+  if (attach_counter++ != 0)
+    return;
+
+  expander_error_ = initExpander();
+}
+
 }
 }

src/kaleidoscope/hardware/ErgoDoxScanner.h

@@ -40,8 +40,9 @@ class ErgoDoxScanner {
   void unselectRows();
   uint8_t readCols(int row);
 
+  void reattachExpanderOnError();
+
  private:
-  bool i2c_initialized_ = false;
   uint8_t expander_error_ = 0x20;
 
   uint8_t initExpander();