Cache status value in the driver

src/ds323x/configuration.rs

@@ -33,24 +33,20 @@ where
     }
 
     /// Enable the 32kHz output.
-    ///
-    /// (Does not alter the device register if already enabled).
     pub fn enable_32khz_output(&mut self) -> Result<(), Error<E>> {
-        let status = self.iface.read_register(Register::STATUS)?;
+        // avoid clearing alarm flags
-        if (status & BitFlags::EN32KHZ) == 0 {
+        let status = self.status | BitFlags::EN32KHZ | BitFlags::ALARM2F | BitFlags::ALARM1F;
-            self.iface.write_register(Register::STATUS, status | BitFlags::EN32KHZ)?;
+        self.iface.write_register(Register::STATUS, status)?;
-        }
+        self.status = status;
         Ok(())
     }
 
     /// Disable the 32kHz output.
-    ///
-    /// (Does not alter the device register if already disabled).
     pub fn disable_32khz_output(&mut self) -> Result<(), Error<E>> {
-        let status = self.iface.read_register(Register::STATUS)?;
+        // avoid clearing alarm flags
-        if (status & BitFlags::EN32KHZ) != 0 {
+        let status = self.status & !BitFlags::EN32KHZ | BitFlags::ALARM2F | BitFlags::ALARM1F;
-            self.iface.write_register(Register::STATUS, status & !BitFlags::EN32KHZ)?;
+        self.iface.write_register(Register::STATUS, status)?;
-        }
+        self.status = status;
         Ok(())
     }
 

src/lib.rs

@@ -401,9 +401,12 @@ impl BitFlags {
     const RS2        : u8 = 0b0001_0000;
     const RS1        : u8 = 0b0000_1000;
     const INTCN      : u8 = 0b0000_0100;
-    const BUSY       : u8 = 0b0000_0100;
-    const EN32KHZ    : u8 = 0b0000_1000;
     const OSC_STOP   : u8 = 0b1000_0000;
+    const BB32KHZ    : u8 = 0b0100_0000;
+    const EN32KHZ    : u8 = 0b0000_1000;
+    const BUSY       : u8 = 0b0000_0100;
+    const ALARM2F    : u8 = 0b0000_0010;
+    const ALARM1F    : u8 = 0b0000_0001;
 }
 
 const DEVICE_ADDRESS   : u8 = 0b110_1000;
@@ -426,6 +429,7 @@ use interface::{ I2cInterface, SpiInterface };
 pub struct Ds323x<DI, IC> {
     iface: DI,
     control: u8,
+    status : u8,
     _ic: PhantomData<IC>
 }
 
@@ -435,11 +439,13 @@ where
 {
     /// Create a new instance of the DS3231 device.
     pub fn new_ds3231(i2c: I2C) -> Self {
+        const STATUS_POR_VALUE : u8 = BitFlags::OSC_STOP | BitFlags::EN32KHZ;
         Ds323x {
             iface: I2cInterface {
                 i2c,
             },
             control: CONTROL_POR_VALUE,
+            status: STATUS_POR_VALUE,
             _ic: PhantomData
         }
     }
@@ -456,11 +462,13 @@ where
 {
     /// Create a new instance of the DS3232 device.
     pub fn new_ds3232(i2c: I2C) -> Self {
+        const STATUS_POR_VALUE : u8 = BitFlags::OSC_STOP | BitFlags::BB32KHZ | BitFlags::EN32KHZ;
         Ds323x {
             iface: I2cInterface {
                 i2c,
             },
             control: CONTROL_POR_VALUE,
+            status: STATUS_POR_VALUE,
             _ic: PhantomData
         }
     }
@@ -478,12 +486,14 @@ where
 {
     /// Create a new instance.
     pub fn new_ds3234(spi: SPI, chip_select: CS) -> Self {
+        const STATUS_POR_VALUE : u8 = BitFlags::OSC_STOP | BitFlags::BB32KHZ | BitFlags::EN32KHZ;
         Ds323x {
             iface: SpiInterface {
                 spi,
                 cs: chip_select
             },
             control: CONTROL_POR_VALUE,
+            status: STATUS_POR_VALUE,
             _ic: PhantomData
         }
     }

tests/common/mod.rs

@@ -7,6 +7,10 @@ use hal::spi::{ Mock as SpiMock, Transaction as SpiTrans };
 pub const DEVICE_ADDRESS   : u8 = 0b110_1000;
 #[allow(unused)]
 pub const CONTROL_POR_VALUE: u8 = 0b0001_1100;
+#[allow(unused)]
+pub const DS3231_POR_STATUS: u8 = BitFlags::OSC_STOP | BitFlags::EN32KHZ;
+#[allow(unused)]
+pub const DS323X_POR_STATUS: u8 = BitFlags::OSC_STOP | BitFlags::BB32KHZ | BitFlags::EN32KHZ;
 
 pub struct Register;
 
@@ -34,9 +38,12 @@ impl BitFlags {
     pub const RS2        : u8 = 0b0001_0000;
     pub const RS1        : u8 = 0b0000_1000;
     pub const INTCN      : u8 = 0b0000_0100;
-    pub const BUSY       : u8 = 0b0000_0100;
-    pub const EN32KHZ    : u8 = 0b0000_1000;
     pub const OSC_STOP   : u8 = 0b1000_0000;
+    pub const BB32KHZ    : u8 = 0b0100_0000;
+    pub const EN32KHZ    : u8 = 0b0000_1000;
+    pub const BUSY       : u8 = 0b0000_0100;
+    pub const ALARM2F    : u8 = 0b0000_0010;
+    pub const ALARM1F    : u8 = 0b0000_0001;
 }
 
 pub struct DummyOutputPin;

tests/configuration.rs

@@ -10,7 +10,8 @@ use ds323x::SqWFreq;
 mod common;
 use common::{ DEVICE_ADDRESS as DEV_ADDR, Register, new_ds3231,
               new_ds3232, new_ds3234, destroy_ds3231, destroy_ds3232,
-              destroy_ds3234, BitFlags as BF, CONTROL_POR_VALUE };
+              destroy_ds3234, BitFlags as BF, CONTROL_POR_VALUE,
+              DS3231_POR_STATUS, DS323X_POR_STATUS };
 
 macro_rules! call_triple_test {
     ($name:ident, $method:ident, $i2c_transactions:expr, $spi_transactions:expr) => {
@@ -31,6 +32,19 @@ macro_rules! call_method_test {
     };
 }
 
+macro_rules! call_method_status_test {
+    ($name:ident, $method:ident, $value_ds3231:expr, $value_ds323x:expr) => {
+        mod $name {
+            use super::*;
+            call_test!(can_call_ds3231, $method, new_ds3231, destroy_ds3231,
+                [ I2cTrans::write(DEV_ADDR, vec![Register::STATUS, $value_ds3231]) ]);
+            call_test!(can_call_ds3232, $method, new_ds3232, destroy_ds3232,
+                [ I2cTrans::write(DEV_ADDR, vec![Register::STATUS, $value_ds323x]) ]);
+            call_test!(can_call_ds3234, $method, new_ds3234, destroy_ds3234,
+                [ SpiTrans::write(vec![Register::STATUS + 0x80, $value_ds323x]) ]);
+        }
+    };
+}
 
 macro_rules! change_if_necessary_test {
     ($name:ident, $method:ident, $register:ident, $value_enabled:expr, $value_disabled:expr) => {
@@ -52,8 +66,12 @@ macro_rules! change_if_necessary_test {
 
 call_method_test!(enable, enable, CONTROL, CONTROL_POR_VALUE & !BF::EOSC);
 call_method_test!(disable, disable, CONTROL, CONTROL_POR_VALUE | BF::EOSC);
-change_if_necessary_test!(en_32khz_out,  enable_32khz_output,  STATUS, BF::EN32KHZ, 0);
+call_method_status_test!(en_32khz_out,  enable_32khz_output,
-change_if_necessary_test!(dis_32khz_out, disable_32khz_output, STATUS, 0xFF & !BF::EN32KHZ, 0xFF);
+    DS3231_POR_STATUS |  BF::EN32KHZ | BF::ALARM2F | BF::ALARM1F,
+    DS323X_POR_STATUS |  BF::EN32KHZ | BF::ALARM2F | BF::ALARM1F);
+call_method_status_test!(dis_32khz_out, disable_32khz_output,
+    DS3231_POR_STATUS & !BF::EN32KHZ | BF::ALARM2F | BF::ALARM1F,
+    DS323X_POR_STATUS & !BF::EN32KHZ | BF::ALARM2F | BF::ALARM1F);
 change_if_necessary_test!(clr_stop, clear_has_been_stopped_flag, STATUS, 0xFF & !BF::OSC_STOP, 0xFF);
 change_if_necessary_test!(conv_temp, convert_temperature, CONTROL, CONTROL_POR_VALUE | BF::TEMP_CONV, CONTROL_POR_VALUE & !BF::TEMP_CONV);