ad5680: idle low for powersaving

src/ad5680.rs

@@ -25,7 +25,7 @@ pub struct Dac<SPI: Transfer<u8>, S: OutputPin> {
 
 impl<SPI: Transfer<u8>, S: OutputPin> Dac<SPI, S> {
     pub fn new(spi: SPI, mut sync: S) -> Self {
-        let _ = sync.set_high();
+        let _ = sync.set_low();
         
         Dac {
             spi,
@@ -34,11 +34,14 @@ impl<SPI: Transfer<u8>, S: OutputPin> Dac<SPI, S> {
     }
 
     fn write(&mut self, mut buf: [u8; 3]) -> Result<(), SPI::Error> {
-        let _ = self.sync.set_low();
-        let result = self.spi.transfer(&mut buf);
+        // pulse sync to start a new transfer. leave sync idle low
+        // afterwards to save power as recommended per datasheet.
         let _ = self.sync.set_high();
+        cortex_m::asm::nop();
+        let _ = self.sync.set_low();
 
-        result.map(|_| ())
+        self.spi.transfer(&mut buf)?;
+        Ok(())
     }
 
     /// value: `0..0x20_000`

src/main.rs

@@ -144,7 +144,7 @@ fn main() -> ! {
                                             let ref_adc_data = channels.read_ref_adc(channel);
                                             let state = channels.channel_state(channel);
                                             let _ = writeln!(
-                                                socket, "t={} raw{}=0x{:06X} ref_adc={}",
+                                                socket, "t={} raw{}=0x{:06X} ref_adc=0x{:X}",
                                                 state.adc_time, channel, adc_data,
                                                 ref_adc_data
                                             );

src/pins.rs

@@ -35,7 +35,7 @@ impl ChannelPins for Channel0 {
     type DacSync = PE4<Output<PushPull>>;
     type Shdn = PE10<Output<PushPull>>;
     type RefAdc = Adc<ADC1>;
-    type RefPin = PA0<Analog>;
+    type RefPin = PA4<Analog>;
 }
 
 impl ChannelPins for Channel1 {
@@ -43,7 +43,7 @@ impl ChannelPins for Channel1 {
     type DacSync = PF6<Output<PushPull>>;
     type Shdn = PE15<Output<PushPull>>;
     type RefAdc = Adc<ADC2>;
-    type RefPin = PA3<Analog>;
+    type RefPin = PA5<Analog>;
 }
 
 /// SPI peripheral used for communication with the ADC
@@ -108,7 +108,7 @@ impl Pins {
         let _ = shdn0.set_low();
         let mut ref0_adc = Adc::adc1(adc1, true, Default::default());
         ref0_adc.enable();
-        let ref0_pin = gpioa.pa0.into_analog();
+        let ref0_pin = gpioa.pa4.into_analog();
         let channel0 = ChannelPinSet {
             dac_spi: dac0_spi,
             dac_sync: dac0_sync,
@@ -125,7 +125,7 @@ impl Pins {
         let _ = shdn1.set_low();
         let mut ref1_adc = Adc::adc2(adc2, true, Default::default());
         ref1_adc.enable();
-        let ref1_pin = gpioa.pa3.into_analog();
+        let ref1_pin = gpioa.pa5.into_analog();
         let channel1 = ChannelPinSet {
             dac_spi: dac1_spi,
             dac_sync: dac1_sync,