Update initialize

Author: PaulZC

src/SparkFun_Qwiic_KX13X.cpp

@@ -99,27 +99,58 @@ bool QwDevKX13X::initialize(uint8_t settings)
 //
 // Resets the accelerometer
 //
-// To change the value of the SRST bit, the PC1 bit in CNTL1 register must first be set to 0.
+// Kionix Technical Reference Manual says:
+// "To change the value of the SRST bit, the PC1 bit in CNTL1 register must first be set to 0."
 //
+// Kionix TN027 "Power On Procedure" says to:
+//   Write 0x00 to register 0x7F
+//   Write 0x00 to CNTL2
+//   Write 0x80 (SRST) to CNTL2
+//
+// Kionix Technical Reference Manual says:
+// "For I2C Communication: Setting SRST = 1 will NOT result in an ACK, since the part immediately
+//  enters the RAM reboot routine. NACK may be used to confirm this command."
+// However, we've not seen the NACK when writing the SRST bit. That write always seems to be ACK'd as normal.
+// But, the _next_ I2C transaction _does_ get NACK'd...
+// The solution seems to be to keep trying to read CNTL2 and wait for the SRST bit to be cleared.
+
 bool QwDevKX13X::softwareReset()
 {
   enableAccel(false); // Clear the PC1 bit in CNTL1
 
+  int retVal;
+
+  retVal = writeRegisterByte(0x7F, 0);
+
+  if (retVal != 0)
+    return false;
+
+  retVal = writeRegisterByte(SFE_KX13X_CNTL2, 0);
+
+  if (retVal != 0)
+    return false;
+
   sfe_kx13x_cntl2_bitfield_t cntl2;
   cntl2.all = 0;
   cntl2.bits.srst = 1; // This is a long winded, but definitive way of setting the software reset bit
 
-  int retVal;
+  retVal = writeRegisterByte(SFE_KX13X_CNTL2, cntl2.all); // Do the reset
 
-  retVal = writeRegisterByte(SFE_KX13X_CNTL2, cntl2.all);
+  uint8_t loopCount = 0;
+  while (loopCount < 10) // Reset takes about 2ms. Timeout after 10ms
+  {
+    retVal = readRegisterRegion(SFE_KX13X_CNTL2, &cntl2.all, 1); // Try to read CNTL2 (the first read gets NACK'd)
 
-  // Logic is inverted here - if we reset using I2C the
-  // accelerometer immediately shuts off which results
-  // in a NACK.
-  if (retVal != 0)
-    return true;
+    if ((retVal == 0) && (cntl2.bits.srst == 0)) // Check if the software reset bit has been cleared
+      loopCount = 10; // Exit the loop if it has
+    else
+    {
+      loopCount++; // Increment the count and repeat
+      delay(1); // Delay for 1ms: important for SPI
+    }
+  }
 
-  return false;
+  return ((retVal == 0) && (cntl2.bits.srst == 0));
 }
 
 //////////////////////////////////////////////////