From f5d8ee3fef87ecdb5811591ec3af841d5ee33ee3 Mon Sep 17 00:00:00 2001
From: occheung <dc@m-labs.hk>
Date: Fri, 6 Sep 2024 16:25:55 +0800
Subject: [PATCH] io_expander: check I2C (n)ack on write

---
 src/libboard_artiq/src/io_expander.rs | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/libboard_artiq/src/io_expander.rs b/src/libboard_artiq/src/io_expander.rs
index 55a1694..7b8aa51 100644
--- a/src/libboard_artiq/src/io_expander.rs
+++ b/src/libboard_artiq/src/io_expander.rs
@@ -111,9 +111,15 @@ impl IoExpander {
 
     fn write(&self, i2c: &mut i2c::I2c, addr: u8, value: u8) -> Result<(), &'static str> {
         i2c.start()?;
-        i2c.write(self.address)?;
-        i2c.write(addr)?;
-        i2c.write(value)?;
+        if !i2c.write(self.address)? {
+            return Err("io expander failed to ack control byte (read)");
+        }
+        if !i2c.write(addr)? {
+            return Err("io expander failed to ack register address");
+        }
+        if !i2c.write(value)? {
+            return Err("io expander failed to ack value");
+        }
         i2c.stop()?;
         Ok(())
     }