HM 10 Pinout

No	Name	Description
1	UART_TX	UART Interface
2	UART_RX	UART Interface
3	UART_CTS	UART Interface
4	UART_RTS	UART Interface
5	NC	No connection
6	NC	No connection
7	NC	No connection
8	NC	No connection
9	NC	No connection
10	NC	No connection
11	RESETB	Reset if low longer than 100ms
12	VCC	3.3v
13	GND	Ground
14	GND	Ground
15	USB_D-	USB interface
16	NC	No connection
17	NC	No connection
18	NC	No connection
19	NC	No connection
20	USB_D+	USB Interface
21	GND	Ground
22	GND	Ground
23	PIO0	System key
23	PIO1	System LED
24	PIO2	Programmable input/output line
25	PIO3	Programmable input/output line
26	PIO4	Programmable input/output line
27	PIO5	Programmable input/output line
28	PIO6	Programmable input/output line
29	PIO7	Programmable input/output line
30	PIO8	Programmable input/output line
31	PIO9	Programmable input/output line
32	PI10	Programmable input/output line
33	PI11	Programmable input/output line
34	PI12	Programmable input/output line

Pulled from the datasheet. Other sources claim that some of the unconnected pins are PCM audio pins, but this is likely a mistake; the CC2540 does not have audio capabilities. It's possible the site simply typed in the pins from another TI CC2xxx chip that does.