kentry.c

   1 #include "stm32f411.h"
   2
   3 static const char *text[] = {
   4   "hello, friend.\r\n",
   5   "hello, friend?\r\n",
   6   "that's lame.\r\n",
   7   "maybe i should give you a name.\r\n",
   8   "but that's a slippery slope.\r\n",
   9   "you're only in my head.\r\n",
  10   "we have to remember that.\r\n",
  11   "shit.\r\n",
  12   "it's actually happening, i'm talking to an imaginary person.\r\n\n"
  13 };
  14
  15 void
  16 kentry (void)
  17 {
  18   unsigned int line, off;
  19
  20   /*  Test UART and LED  ----------------------------------------------------  */
  21
  22   while (1)
  23     {
  24       for (line = 0; line < sizeof text / sizeof *text; ++line)
  25         {
  26           /* Print current line  */
  27           off = 0;
  28           while (text[line][off])
  29             {
  30               /* TXE: Transmit data register empty  */
  31               while (!(*USART1_SR & (1u << 7))); /* 0: Data is not transferred
  32                                                     to the shift register  */
  33
  34               /* DR[8:0]: Data value  */
  35               *USART1_DR = text[line][off++];
  36             }
  37
  38           /* TC: Transmission complete  */
  39           while (!(*USART1_SR & (1u << 6))); /* 0: Transmission is not
  40                                                 complete  */
  41
  42           /* Blink LED  */
  43           *GPIOC_ODR ^= (1u << 13);
  44         }
  45     }
  46 }