Using USBSerial on BLACKPILL board.

For more details click on the link below:

Import programBlackpill_Hello

Using low cost Blackpill (STM32F411CEU6) boards with mbed.

Revision:
0:2912fe6f7530
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed_app.json	Sat Jan 30 11:18:14 2021 +0000
@@ -0,0 +1,8 @@
+{
+    "target_overrides":{
+        "*": {
+            "target.clock_source": "USE_PLL_HSE_XTAL",
+            "target.clock_source_usb": "1"
+        }
+    }
+}