From ff4a46c278408673ab1dc687e75b880b14916607 Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Sat, 5 Mar 2016 00:16:12 +0800
Subject: [PATCH] runtime/i2c: make syscalls more ARTIQ-Python-friendly

---
 artiq/coredevice/exceptions.py |  4 ++++
 artiq/runtime/i2c.c            | 13 ++++++-------
 artiq/runtime/i2c.h            |  6 +++---
 3 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/artiq/coredevice/exceptions.py b/artiq/coredevice/exceptions.py
index 05d9d1c29..36314ed1a 100644
--- a/artiq/coredevice/exceptions.py
+++ b/artiq/coredevice/exceptions.py
@@ -113,3 +113,7 @@ class DDSBatchError(Exception):
     or when too many commands are batched.
     """
     artiq_builtin = True
+
+class I2CError(Exception):
+    """Raised with a I2C transaction fails."""
+    artiq_builtin = True
diff --git a/artiq/runtime/i2c.c b/artiq/runtime/i2c.c
index af8b9bed7..b1cfb733a 100644
--- a/artiq/runtime/i2c.c
+++ b/artiq/runtime/i2c.c
@@ -1,5 +1,6 @@
 #include <generated/csr.h>
 
+#include "artiq_personality.h"
 #include "rtio.h"
 #include "i2c.h"
 
@@ -91,7 +92,7 @@ static void i2c_scl_o(int busno, int o) {}
 #endif
 
 
-int i2c_init(int busno)
+void i2c_init(int busno)
 {
     /* Set SCL as output, and high level */
     i2c_scl_o(busno, 1);
@@ -104,10 +105,8 @@ int i2c_init(int busno)
     /* Check the I2C bus is ready */
     i2c_halfperiod();
     i2c_halfperiod();
-    if(i2c_sda_i(busno))
-        return 1; /* success */
-    else
-        return 0;
+    if(!i2c_sda_i(busno))
+        artiq_raise_from_c("I2CError", "SDA is stuck low")
 }
 
 void i2c_start(int busno)
@@ -132,7 +131,7 @@ void i2c_stop(int busno)
     i2c_halfperiod();
 }
 
-int i2c_write(int busno, char b)
+int i2c_write(int busno, int b)
 {
     int i;
 
@@ -158,7 +157,7 @@ int i2c_write(int busno, char b)
     return !i2c_sda_i(busno);
 }
 
-char i2c_read(int busno, int ack)
+int i2c_read(int busno, int ack)
 {
     int i;
     char b;
diff --git a/artiq/runtime/i2c.h b/artiq/runtime/i2c.h
index b30e25706..c7aab6e22 100644
--- a/artiq/runtime/i2c.h
+++ b/artiq/runtime/i2c.h
@@ -1,10 +1,10 @@
 #ifndef __I2C_H
 #define __I2C_H
 
-int i2c_init(int busno);
+void i2c_init(int busno);
 void i2c_start(int busno);
 void i2c_stop(int busno);
-int i2c_write(int busno, char b);
-char i2c_read(int busno, int ack);
+int i2c_write(int busno, int b);
+int i2c_read(int busno, int ack);
 
 #endif