From f1a58b781164bf2764c264feeaa9aaed1143b69c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Robert=20J=C3=B6rdens?= <rj@quartiq.de>
Date: Tue, 25 May 2021 15:21:09 +0000
Subject: [PATCH] pounder: simplify attenuator spi interface

---
 src/hardware/pounder/attenuators.rs | 19 ++++++++-----------
 src/hardware/pounder/mod.rs         | 21 ++-------------------
 2 files changed, 10 insertions(+), 30 deletions(-)

diff --git a/src/hardware/pounder/attenuators.rs b/src/hardware/pounder/attenuators.rs
index 156da9f..092338e 100644
--- a/src/hardware/pounder/attenuators.rs
+++ b/src/hardware/pounder/attenuators.rs
@@ -30,16 +30,16 @@ pub trait AttenuatorInterface {
         // Read all the channels, modify the channel of interest, and write all the channels back.
         // This ensures the staging register and the output register are always in sync.
         let mut channels = [0_u8; 4];
-        self.read_all_attenuators(&mut channels)?;
+        self.transfer_attenuators(&mut channels)?;
 
         // The lowest 2 bits of the 8-bit shift register on the attenuator are ignored. Shift the
         // attenuator code into the upper 6 bits of the register value. Note that the attenuator
         // treats inputs as active-low, so the code is inverted before writing.
         channels[channel as usize] = (!attenuation_code) << 2;
-        self.write_all_attenuators(&channels)?;
+        self.transfer_attenuators(&mut channels)?;
 
         // Finally, latch the output of the updated channel to force it into an active state.
-        self.latch_attenuators(channel)?;
+        self.latch_attenuator(channel)?;
 
         Ok(attenuation_code as f32 / 2.0)
     }
@@ -57,8 +57,8 @@ pub trait AttenuatorInterface {
         // Reading the data always shifts data out of the staging registers, so we perform a
         // duplicate write-back to ensure the staging register is always equal to the output
         // register.
-        self.read_all_attenuators(&mut channels)?;
-        self.write_all_attenuators(&channels)?;
+        self.transfer_attenuators(&mut channels)?;
+        self.transfer_attenuators(&mut channels)?;
 
         // The attenuation code is stored in the upper 6 bits of the register, where each LSB
         // represents 0.5 dB. The attenuator stores the code as active-low, so inverting the result
@@ -74,13 +74,10 @@ pub trait AttenuatorInterface {
 
     fn reset_attenuators(&mut self) -> Result<(), Error>;
 
-    fn latch_attenuators(&mut self, channel: Channel) -> Result<(), Error>;
-    fn read_all_attenuators(
+    fn latch_attenuator(&mut self, channel: Channel) -> Result<(), Error>;
+
+    fn transfer_attenuators(
         &mut self,
         channels: &mut [u8; 4],
     ) -> Result<(), Error>;
-    fn write_all_attenuators(
-        &mut self,
-        channels: &[u8; 4],
-    ) -> Result<(), Error>;
 }
diff --git a/src/hardware/pounder/mod.rs b/src/hardware/pounder/mod.rs
index 32a8e80..dd5ce95 100644
--- a/src/hardware/pounder/mod.rs
+++ b/src/hardware/pounder/mod.rs
@@ -344,7 +344,7 @@ impl AttenuatorInterface for PounderDevices {
     ///
     /// Args:
     /// * `channel` - The attenuator channel to latch.
-    fn latch_attenuators(&mut self, channel: Channel) -> Result<(), Error> {
+    fn latch_attenuator(&mut self, channel: Channel) -> Result<(), Error> {
         let pin = match channel {
             Channel::In0 => ATT_LE0_PIN,
             Channel::In1 => ATT_LE2_PIN,
@@ -368,7 +368,7 @@ impl AttenuatorInterface for PounderDevices {
     ///
     /// Args:
     /// * `channels` - A slice to store the channel readings into.
-    fn read_all_attenuators(
+    fn transfer_attenuators(
         &mut self,
         channels: &mut [u8; 4],
     ) -> Result<(), Error> {
@@ -378,23 +378,6 @@ impl AttenuatorInterface for PounderDevices {
 
         Ok(())
     }
-
-    /// Write the attenuator shift registers.
-    ///
-    /// Args:
-    /// * `channels` - The data to write into the attenuators.
-    fn write_all_attenuators(
-        &mut self,
-        channels: &[u8; 4],
-    ) -> Result<(), Error> {
-        let mut result = [0_u8; 4];
-        result.clone_from_slice(channels);
-        self.attenuator_spi
-            .transfer(&mut result)
-            .map_err(|_| Error::Spi)?;
-
-        Ok(())
-    }
 }
 
 impl PowerMeasurementInterface for PounderDevices {