Slim serial number to hex string conversion

Author: sandeepmistry

cores/arduino/USB/USBCore.cpp

@@ -177,6 +177,24 @@ uint32_t USBDeviceClass::sendConfiguration(uint32_t maxlen)
 	return true;
 }
 
+static void utox(uint32_t val, char* s) {
+	// lead zero pad
+	for (uint32_t i = 0x10000000; i > 1; i = i >> 4) {
+		if (val < i) {
+			*s++ = '0';
+		}
+	}
+
+	// convert value to hex string
+	utoa(val, s, 16);
+
+	// make string uppercase
+	while (s && *s) {
+		*s = toupper(*s);
+		s++;
+	}
+}
+
 bool USBDeviceClass::sendDescriptor(USBSetup &setup)
 {
 	uint8_t t = setup.wValueH;
@@ -228,7 +246,11 @@ bool USBDeviceClass::sendDescriptor(USBSetup &setup)
 			#define SERIAL_NUMBER_WORD_3	*(volatile uint32_t*)(0x0080A048)
 
 			char name[ISERIAL_MAX_LEN];
-			sprintf(name, "%8X%8X%8X%8X", SERIAL_NUMBER_WORD_0, SERIAL_NUMBER_WORD_1, SERIAL_NUMBER_WORD_2, SERIAL_NUMBER_WORD_3);
+			utox(SERIAL_NUMBER_WORD_0, &name[0]);
+			utox(SERIAL_NUMBER_WORD_1, &name[8]);
+			utox(SERIAL_NUMBER_WORD_2, &name[16]);
+			utox(SERIAL_NUMBER_WORD_3, &name[24]);
+
 			PluggableUSB().getShortName(&name[32]);
 			return sendStringDescriptor((uint8_t*)name, setup.wLength);
 #endif