Adding nonblocking USART transmit, usart_tx().

Other USART transmission functions are still blocking, but are now
implemented in terms of usart_tx().

2 files changed, 42 insertions, 23 deletions

diff --git a/libmaple/usart.c b/libmaple/usart.c
index 22542fd..fbd4d70 100644
--- a/libmaple/usart.c
+++ b/libmaple/usart.c
@@ -26,6 +26,8 @@
 
 /**
  * @file usart.c
+ * @author Marti Bolivar <mbolivar@leaflabs.com,
+ *         Perry Hung <perry@leaflabs.com>
  * @brief USART control routines
  */
 
@@ -158,7 +160,7 @@ void usart_disable(usart_dev *dev) {
  *  @brief Call a function on each USART.
  *  @param fn Function to call.
  */
-void usart_foreach(void (*fn)(usart_dev *dev)) {
+void usart_foreach(void (*fn)(usart_dev*)) {
     fn(USART1);
     fn(USART2);
     fn(USART3);
@@ -169,20 +171,27 @@ void usart_foreach(void (*fn)(usart_dev *dev)) {
 }
 
 /**
- * @brief Print a null-terminated string to the specified serial port.
- * @param dev Serial port to send the string on
- * @param str String to send
+ * @brief Nonblocking USART transmit
+ * @param dev Serial port to transmit over
+ * @param buf Buffer to transmit
+ * @param len Maximum number of bytes to transmit
+ * @return Number of bytes transmitted
  */
-void usart_putstr(usart_dev *dev, const char* str) {
-    char ch;
-
-    while ((ch = *(str++)) != '\0') {
-        usart_putc(dev, ch);
+uint32 usart_tx(usart_dev *dev, const uint8 *buf, uint32 len) {
+    usart_reg_map *regs = dev->regs;
+    uint32 txed = 0;
+    while ((regs->SR & USART_SR_TXE) && (txed < len)) {
+        regs->DR = buf[txed++];
     }
+    return txed;
 }
 
 /**
- * @brief Print an unsigned integer to the specified serial port.
+ * @brief Transmit an unsigned integer to the specified serial port in
+ *        decimal format.
+ *
+ * This function blocks until the integer's digits have been
+ * completely transmitted.
  *
  * @param dev Serial port to send on
  * @param val Number to print
diff --git a/libmaple/usart.h b/libmaple/usart.h
index 02f23da..b2bb034 100644
--- a/libmaple/usart.h
+++ b/libmaple/usart.h
@@ -26,6 +26,8 @@
 
 /**
  * @file usart.h
+ * @author Marti Bolivar <mbolivar@leaflabs.com>,
+ *         Perry Hung <perry@leaflabs.com>
  * @brief USART definitions and prototypes
  */
 
@@ -251,20 +253,12 @@ extern usart_dev *UART4;
 extern usart_dev *UART5;
 #endif
 
-#ifdef STM32_MEDIUM_DENSITY
-#define NR_USARTS 3
-#elif defined(STM32_HIGH_DENSITY)
-#define NR_USARTS 5
-#else
-#warn "Only medium and high density devices are currently supported"
-#endif
-
 void usart_init(usart_dev *dev);
 void usart_set_baud_rate(usart_dev *dev, uint32 clock_speed, uint32 baud);
 void usart_enable(usart_dev *dev);
 void usart_disable(usart_dev *dev);
 void usart_foreach(void (*fn)(usart_dev *dev));
-void usart_putstr(usart_dev *dev, const char*);
+uint32 usart_tx(usart_dev *dev, const uint8 *buf, uint32 len);
 void usart_putudec(usart_dev *dev, uint32 val);
 
 /**
@@ -276,16 +270,32 @@ static inline void usart_disable_all(void) {
 
 /**
  * @brief Transmit one character on a serial port.
+ *
+ * This function blocks until the character has been successfully
+ * transmitted.
+ *
  * @param dev Serial port to send on.
  * @param byte Byte to transmit.
  */
 static inline void usart_putc(usart_dev* dev, uint8 byte) {
-    usart_reg_map *regs = dev->regs;
-
-    while ((regs->SR & USART_SR_TXE) == 0)
+    uint8 buf[] = {byte};
+    while (!usart_tx(dev, buf, 1))
         ;
+}
 
-    regs->DR = byte;
+/**
+ * @brief Transmit a character string on a serial port.
+ *
+ * This function blocks until str is completely transmitted.
+ *
+ * @param dev Serial port to send on
+ * @param str String to send
+ */
+static inline void usart_putstr(usart_dev *dev, const char* str) {
+    uint32 i = 0;
+    while (str[i] != '\0') {
+        usart_putc(dev, str[i]);
+    }
 }
 
 /**