Things to support
HFP spec is rather painful to implement as there is a lot of stuff mandatory. As per HFP 1.5 the following list of items are mandatory.
1. Connection management
Service Level Connection establishment 4.2
Service Level Connection release 4.3
2. Phone status information
Transfer of Registration Status 4.4
Transfer of Signal Strength Indication 4.5
Transfer of Roaming Status Indication 4.6
Transfer of Battery Level Indication 4.7
Query of Operator Selection 4.8
Extended Audio Gateway Error Codes 4.9
Transfer of Call, Call Setup and Call Held 4.10 Status
3. Audio Connection handling
Audio Connection set up 4.11
Audio Connection release 4.12
4 Accept an incoming voice call
Answer an incoming call 4.13
6. Terminate a call
Terminate a call process 4.15
7. Audio Connection transfer during an ongoing call
Audio Connection transfer towards the HF 4.16
Audio Connection transfer towards the AG 4.17
8. Place a call with a phone number supplied by the HF
Place a call with the phone number supplied by the HF 4.18
9. Place a call using memory dialing
Memory dialing from the HF 4.19
10. Place a call to the last number dialed
Last number re-dial from the HF 4.20
11. Call waiting notification
Call waiting notification activation 4.21
13. Calling Line Identification (CLI)
Calling Line Identification (CLI) notification 4.23
17. Ability to transmit DTMF codes
Transmit DTMF code 4.27
20. Subscriber Number Information
Subscriber Number Information 4.30
21a. Enhanced Call Status
Query Call List 4.31
Indication of Held Call Status 4.31
Required interfaces with other subsystems to support HFP features
- Telephony subsystem: for most of the call related features
- Power Management Unit: for Battery Level
