From 87894102e504d8cd24f20dde1a1e619d851c42a2 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Thu, 28 Nov 2019 17:49:02 +0800
Subject: [PATCH] si549: use recommended i2c read sequence

---
 artiq/firmware/libboard_artiq/wrpll.rs | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/artiq/firmware/libboard_artiq/wrpll.rs b/artiq/firmware/libboard_artiq/wrpll.rs
index 0a075beff..d27b90767 100644
--- a/artiq/firmware/libboard_artiq/wrpll.rs
+++ b/artiq/firmware/libboard_artiq/wrpll.rs
@@ -105,16 +105,6 @@ mod i2c {
         half_period();
     }
 
-    pub fn restart(dcxo: Dcxo) {
-        // Set SCL low then SDA high */
-        scl_o(dcxo, false);
-        half_period();
-        sda_oe(dcxo, false);
-        half_period();
-        // Do a regular start
-        start(dcxo);
-    }
-
     pub fn stop(dcxo: Dcxo) {
         // First, make sure SCL is low, so that the target releases the SDA line
         scl_o(dcxo, false);
@@ -223,12 +213,15 @@ mod si549 {
         if !i2c::write(dcxo, reg) {
             return Err("Si549 failed to ack register")
         }
-        i2c::restart(dcxo);
+        i2c::stop(dcxo);
+
+        i2c::start(dcxo);
         if !i2c::write(dcxo, (ADDRESS << 1) | 1) {
             return Err("Si549 failed to ack read address")
         }
         let val = i2c::read(dcxo, false);
         i2c::stop(dcxo);
+
         Ok(val)
     }