From feae22b277e62fdeae54aa1f42206e86e2a44c9e Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Sat, 16 May 2020 01:18:14 +0200
Subject: [PATCH] ad5680: idle low for powersaving

---
 src/ad5680.rs | 11 +++++++----
 src/main.rs   |  2 +-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/ad5680.rs b/src/ad5680.rs
index cc75c95..f550777 100644
--- a/src/ad5680.rs
+++ b/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`
diff --git a/src/main.rs b/src/main.rs
index 06a377c..07e4b92 100644
--- a/src/main.rs
+++ b/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
                                             );