add uart tests

myapps/practice/00-uart-tx/src/main.c

@@ -0,0 +1,21 @@
+// RXD3/TXD3: PA4/PA5
+
+
+#include "CH59x_common.h"
+#include <string.h>
+
+
+int main()
+{
+  char *s = "Hello world\r\n";
+  SetSysClock(CLK_SOURCE_PLL_60MHz);
+  
+  GPIOA_ModeCfg(GPIO_Pin_5, GPIO_ModeOut_PP_5mA);
+  UART3_DefInit();  
+  
+  while (1) {
+    UART3_SendString((uint8_t *)s, strlen(s));
+    mDelaymS(1000);
+  }
+  
+}