nicla-sense-pmic: Use function to toggle Hi-Z mode.

libraries/Nicla_System/src/BQ25120A.h

@@ -4,13 +4,13 @@
 #define BQ25120A_ADDRESS           0x6A
 
 // Register Map
-// https://www.ti.com/lit/ds/symlink/bq25120a.pdf?ts=1610608851953&ref_url=https%253A%252F%252Fwww.startpage.com%252F
+// https://www.ti.com/lit/ds/symlink/bq25120a.pdf
 #define BQ25120A_STATUS             0x00
 #define BQ25120A_FAULTS             0x01
 #define BQ25120A_TS_CONTROL         0x02
 #define BQ25120A_FAST_CHG           0x03
 #define BQ25120A_TERMINATION_CURR   0x04
-#define BQ25120A_BATTERY_CTRL       0x05
+#define BQ25120A_BATTERY_CTRL       0x05 // Battery Voltage Control Register
 #define BQ25120A_SYS_VOUT_CTRL      0x06
 #define BQ25120A_LDO_CTRL           0x07
 #define BQ25120A_PUSH_BUTT_CTRL     0x08
@@ -29,6 +29,21 @@ class BQ25120A
   void writeByte(uint8_t address, uint8_t subAddress, uint8_t data);
   uint8_t readByte(uint8_t address, uint8_t subAddress);
 
+  private:
+  /**
+   * @brief Set the High Impedance Mode Enabled or Disabled.
+   * When enabled, drives the CD pin low to enter high impedance mode.
+   * Note that this only applies when powered with a battery and the condition VIN < VUVLO is met.
+   * When VIN > VUVLO this enables charging instead.
+   * 
+   * When disabled, drives the CD pin high to exit high impedance mode (Active Battery).
+   * When VIN > VUVLO this disables charging.
+   * When exiting this mode, charging resumes if VIN is present, CD is low and charging is enabled.
+   * 
+   * @note The CD pin is internally pulled down.
+   * @param enabled Defines if the high impedance mode should be enabled or disabled.
+   */
+  void setHighImpedanceModeEnabled(bool enabled);
 };
 
 #endif

libraries/Nicla_System/src/pmic_driver.cpp

@@ -4,7 +4,11 @@
 #include "Nicla_System.h"
 #include "DigitalOut.h"
 
-static mbed::DigitalOut cd(p25);
+// Set the CD pin to low to enter high impedance mode
+// Note that this only applies when powered with a battery 
+// and the condition VIN < VUVLO is met.
+// When VIN > VUVLO this enables charging.
+static mbed::DigitalOut cd(p25, 0);
 
 uint8_t BQ25120A::getStatus()
 {
@@ -14,19 +18,19 @@ uint8_t BQ25120A::getStatus()
 
 void BQ25120A::writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
 {
-  cd = 1;
+  setHighImpedanceModeEnabled(false);
   nicla::i2c_mutex.lock();
   Wire1.beginTransmission(address);
   Wire1.write(subAddress);
   Wire1.write(data);
   Wire1.endTransmission();
   nicla::i2c_mutex.unlock();
-  cd = 0;
+  setHighImpedanceModeEnabled(true);
 }
 
 uint8_t BQ25120A::readByte(uint8_t address, uint8_t subAddress)
 {
-  cd = 1;
+  setHighImpedanceModeEnabled(false);
   nicla::i2c_mutex.lock();
   Wire1.beginTransmission(address);
   Wire1.write(subAddress);
@@ -37,6 +41,15 @@ uint8_t BQ25120A::readByte(uint8_t address, uint8_t subAddress)
   while(!Wire1.available() && (millis() - start_time) < timeout) {}
   uint8_t ret = Wire1.read();
   nicla::i2c_mutex.unlock();
-  cd = 0;
+  setHighImpedanceModeEnabled(true);
   return ret;
 }
+
+void BQ25120A::setHighImpedanceModeEnabled(bool enabled) {
+  if(enabled){
+    cd = 0;
+  } else {
+    cd = 1;
+    delayMicroseconds(64); // Give some time to the BQ25120A to wake up
+  }
+}