Merge pull request #50 from asanza/master

Support WRITEC Semihosting command.

Author: jjkt

src/semihost.rs

@@ -82,6 +82,12 @@ pub fn get_semihost_func(start: Instant) -> impl FnMut(&SemihostingCommand) -> S
                     SemihostingResponse::SysIstty { result: Err(-1) }
                 }
             }
+            SemihostingCommand::SysWriteC {ref data} => {
+                // println!("writec: data={:?}", data);
+                print!("{}", *data as char);
+                io::stdout().flush().expect("Could not flush stdout");
+                SemihostingResponse::SysWrite { result: Ok(0) }
+            }
             SemihostingCommand::SysWrite { handle, ref data } => {
                 // println!("write: handle={}, data={:?}", handle, data);
                 if *handle == TT_HANDLE_STDOUT {

zmu_cortex_m/src/semihosting/mod.rs

@@ -107,6 +107,13 @@ pub enum SemihostingCommand {
         handle: u32,
     },
     ///
+    /// Write single char to the debug console
+    /// 
+    SysWriteC {
+        /// char to write
+        data: u8,
+    },
+    ///
     /// Write data to open file handle
     ///
     SysWrite {
@@ -230,6 +237,7 @@ pub enum SemihostingResponse {
 
 const SYS_OPEN: u32 = 0x01;
 const SYS_CLOSE: u32 = 0x02;
+const SYS_WRITEC: u32 = 0x03;
 const SYS_WRITE: u32 = 0x05;
 const SYS_READ: u32 = 0x06;
 const SYS_ISTTY: u32 = 0x09;
@@ -273,6 +281,13 @@ pub fn decode_semihostcmd(
             let handle = processor.read32(params_ptr)?;
             SemihostingCommand::SysClose { handle }
         }
+        SYS_WRITEC => {
+            let params_ptr = r1;
+            let ch = processor.read8(params_ptr)?;
+            SemihostingCommand::SysWriteC {
+                data: ch,
+            }
+        }
         SYS_WRITE => {
             let params_ptr = r1;
             let handle = processor.read32(params_ptr)?;