main: add printing utilities

main.c

@@ -57,6 +57,40 @@ static void wait_10us(uint32_t us10)
 	while (us10--); // burn energy
 }
 
+void putc(char c)
+{
+  while (!UART1->SR.fields.TXE); // wait until TX buffer is empty
+  UART1->DR.reg = c; // put character in buffer to be transmitted
+  // don't wait until the transmission is complete
+}
+
+void puts(const char* s)
+{
+	if (NULL == s) {
+		return;
+	}
+	while (*s) {
+		putc(*s++);
+		IWDG_KR = IWDG_KR_KEY_REFRESH; // reset watchdog
+	}
+}
+
+void putn(uint8_t n)
+{
+	n &= 0x0f; // ensure it's a nibble
+	if (n < 0xa) {
+		putc('0' + n);
+	} else {
+		putc('a' + (n - 0x0a));
+	}
+}
+
+void puth(uint8_t h)
+{
+	putn(h >> 4);
+	putn(h & 0x0f);
+}
+
 // verify (E-)EDID checksums
 // the sum of the bytes (including checksum at the end) must be 0
 static bool checksum_ok(const uint8_t* data, uint16_t length)

main.h

@@ -35,3 +35,12 @@
 
 // address of I²C EEPROM slave device containing EDID information
 #define I2C_SLAVE 0x50
+
+/** print character
+ *  @param[in] c character to print
+ */
+void putc(char c);
+/** print string
+ *  @param[in] s string to print
+ */
+void puts(const char* s);