Two I2C fixes:

1) Bus error will be thrown on read/write errors with errno set. (Read didn't used to fail at all.)
2) try_lock correctly returns boolean whether lock was grabbed.

Fixes #87

2 files changed, 17 insertions, 12 deletions

diff --git a/shared-bindings/nativeio/I2C.c b/shared-bindings/nativeio/I2C.c
index bb827a95d..43cf7b63d 100644
--- a/shared-bindings/nativeio/I2C.c
+++ b/shared-bindings/nativeio/I2C.c
@@ -141,8 +141,7 @@ MP_DEFINE_CONST_FUN_OBJ_1(nativeio_i2c_scan_obj, nativeio_i2c_scan);
 //|     Attempts to grab the I2C lock. Returns True on success.
 //|
 STATIC mp_obj_t nativeio_i2c_obj_try_lock(mp_obj_t self_in) {
-    common_hal_nativeio_i2c_try_lock(MP_OBJ_TO_PTR(self_in));
-    return self_in;
+    return mp_obj_new_bool(common_hal_nativeio_i2c_try_lock(MP_OBJ_TO_PTR(self_in)));
 }
 MP_DEFINE_CONST_FUN_OBJ_1(nativeio_i2c_try_lock_obj, nativeio_i2c_obj_try_lock);
 
@@ -196,7 +195,11 @@ STATIC mp_obj_t nativeio_i2c_readfrom_into(size_t n_args, const mp_obj_t *pos_ar
     } else if (len > bufinfo.len) {
         len = bufinfo.len;
     }
-    common_hal_nativeio_i2c_read(self, args[ARG_address].u_int, ((uint8_t*)bufinfo.buf) + start, len);
+    uint8_t status = common_hal_nativeio_i2c_read(self, args[ARG_address].u_int, ((uint8_t*)bufinfo.buf) + start, len);
+    if (status != 0) {
+        mp_raise_OSError(status);
+    }
+
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_KW(nativeio_i2c_readfrom_into_obj, 3, nativeio_i2c_readfrom_into);
@@ -248,10 +251,10 @@ STATIC mp_obj_t nativeio_i2c_writeto(size_t n_args, const mp_obj_t *pos_args, mp
     }
 
     // do the transfer
-    bool ok = common_hal_nativeio_i2c_write(self, args[ARG_address].u_int,
+    uint8_t status = common_hal_nativeio_i2c_write(self, args[ARG_address].u_int,
         ((uint8_t*) bufinfo.buf) + start, len, args[ARG_stop].u_bool);
-    if (!ok) {
-        nlr_raise(mp_obj_new_exception_msg(&mp_type_OSError, "I2C bus error"));
+    if (status != 0) {
+        mp_raise_OSError(status);
     }
     return mp_const_none;
 }
diff --git a/shared-bindings/nativeio/I2C.h b/shared-bindings/nativeio/I2C.h
index cf7a9fa60..5f3c89a77 100644
--- a/shared-bindings/nativeio/I2C.h
+++ b/shared-bindings/nativeio/I2C.h
@@ -57,12 +57,14 @@ extern void common_hal_nativeio_i2c_unlock(nativeio_i2c_obj_t *self);
 // Probe the bus to see if a device acknowledges the given address.
 extern bool common_hal_nativeio_i2c_probe(nativeio_i2c_obj_t *self, uint8_t addr);
 
-extern bool common_hal_nativeio_i2c_write(nativeio_i2c_obj_t *self, uint16_t address,
-                                          const uint8_t * data, size_t len,
-                                          bool stop);
+// Write to the device and return 0 on success or an appropriate error code from mperrno.h
+extern uint8_t common_hal_nativeio_i2c_write(nativeio_i2c_obj_t *self, uint16_t address,
+                                             const uint8_t * data, size_t len,
+                                             bool stop);
 
-// Reads memory of the i2c device picking up where it left off.
-extern bool common_hal_nativeio_i2c_read(nativeio_i2c_obj_t *self, uint16_t address,
-                                         uint8_t * data, size_t len);
+// Reads memory of the i2c device picking up where it left off and return 0 on
+// success or an appropriate error code from mperrno.h
+extern uint8_t common_hal_nativeio_i2c_read(nativeio_i2c_obj_t *self, uint16_t address,
+                                            uint8_t * data, size_t len);
 
 #endif // __MICROPY_INCLUDED_SHARED_BINDINGS_NATIVEIO_I2C_H__