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added sequence description of the charging process

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uhi22 2022-10-21 13:09:42 +02:00
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@ -99,6 +99,45 @@ Now, in the IDLE shall 3.10.6, the import works:
### Usage on Raspberry
Pcap-ct does not work with Python 3.4. After update to Python 3.8, it works.
## Example flow
This chapter describes the start of a charging session, considering all layers.
Precondition: On charger side, there is a homeplugGP-capable device present, which is configured as CentralCoordinator.
1. The charger creates a "random" value for NID (network ID) and NMK (network membership key), and configures its homeplug modem with these values.
1. The user connects the plug into the car.
2. The car pulls the 12V at CP line to 9V.
3. The charger changes the CP from "permanent high" to "5% PWM".
4. The car wakes up its communication controller and homeplug modem.
5. The car sees coordinator packets on the line, and starts the SLAC sequence by sending SLAC_PARAM.REQ. Can be also two times.
6. The charger receives the SLAC_PARAM.REQ and confirms it with SLAC_PARAM.CNF.
7. The car sends START_ATTEN_CHAR.IND, to start the attenuation measurement. In total 3 times.
8. The car sends MNBC_SOUND.IND, to provide different sounds. In total 10 times.
9. The charger sends ATTEN_CHAR.IND, which contains the number of sounds and for each group the attenuation in dB.
10. The car receives the ATTEN_CHAR.IND. If it would receive multiple of them from different chargers (due to cross-coupling), the car decides based on the attenuation levels, which of the charges is the nearest.
11. The car sends ATTEN_CHAR.RSP to the charger which reported the loudest signals.
12. The car sends SLAC_MATCH.REQ to the charger. It wants to pair with it.
13. The charger responds with SLAC_MATCH.CNF. This contains the self-decided NID (network ID) and NMK (network membership key).
14. The car receives the SLAC_MATCH.CNF, takes the NID and NMK from this message, and configures its homeplug modem with this data.
15. Now, the homeplug modems of the car and of the charger have formed a "private" Homeplug network. The RF traffic can only be decoded by
participants who are using the same NID and NMK.
16. The car wants to know the chargers IP address. In computer networks, a DHCP would be a usual way to do this. In the CCS world, a different
approach is used: SDP, which is the SECC discovery protocol. The DHCP may be also supported as fallback.
17. The car sends a broadcast message "Is here a charger in this network?". Technically, it is an IPv6.UDP.V2GTP.SDP message
with 2 bytes payload, which defines the security level expected by the car. In usual case, the car says "I want unprotected TCP.".
18. The charger receives the SDP request, and sends a SDP response "My IP address is xy, and I support unprotected TCP."
19. The car wants to make sure, that the IP addresses are unique and the relation between IP address and MAC is clear. For
this, it sends a "Neighbour solicitation". (This looks a little bit oversized, because only the participants are in the local network, but
it is standard technology.)
20. The charger responds to the neighbor solicitation request.
21. Now, the car and the charger have a clear view about addressing (MAC, IP).
22. The car requests to open a TCP connection to chargerIP at port 15118.
23. The charger, which was listening on port 15118, confirms the TCP channel.
24. Now, the car and the charger have a reliable, bidirectional TCP channel.
25. The car and the charger use the TCP channel, to exchange V2GTP messages, with EXI content.
26. Todo: Controlled by the content of the EXI messages, the car and the charging are walking through different states to negotiate, start and supervise the charging process.
## Change history / functional status
### 2022-10-19 Communication with Ioniq car established