Proxy

Purpose

The SHC proxy can forward packets between other devices when their distance is too high to have a reliable communication. The proxy doesn't just duplicate all packets automatically (acting as a repeater), but only forwards packets when one of the rules defined in the e2p matches and also translates the device IDs and AES keys. This is to avoid sending unnecessary packets and raising the general risk of collisions. It's assumed that only a small amount of devices can't be reached from the base station typically, so the number of rules is currently limited to 16 and each rule is only for a specific device ID.

Functions, Behavior

The proxy listens for all packets and tries to decrypt them with one of the AES keys defined in e2p. When decryption is successful, Sender ID and Receiver ID are compared to the rules. When they match, the packet is modified according rule definition and sent out using the (most probably differently) defined AES key number from the rule.

Like all other smarthomatic devices, the proxy also sends (roughly once per day) a DeviceInfo message to describe the own Device ID and version. This is always encrypted using the AES key defined in the generic block of the e2p.

In the following example, a device with ID 1045 can be reached form the base station using Device ID 45. The proxy takes the packet and translates between base station and the device. The base station can't reach the device 1045 directly, since it doesn't know its AES key and therefore ignores the original packet in case it would be received despite it's usually too far away to receive it.

Sender IDReceiver IDNew Sender IDNew Receiver IDAES Key Number
045010452
104504500

Example rule configuration from e2p

Supported Messages

  • Generic_DeviceInfo_Status

E2P Device Configuration

OffsetBlockContentTypeSizeDescription
0Hardware
Values for hardware setup, which have no special meaning to SHC device concepts + the DeviceType, which decides about the existence of further blocks.
DeviceTypeEnumValue1 BytesThe device can check with this value if the EEPROM data is meant for the actual type of device. If not, the device goes into an error mode.
Values: 0 = BaseStation, 10 = Proxy, 20 = EnvSensor, 40 = PowerSwitch, 45 = Controller, 50 = RGBDimmer, 60 = Dimmer, 70 = SoilMoistureMeter, 80 = Thermostat, 90 = TeaMaker
8OsccalModeIntValue1 BytesThis value is used to change the speed of the internal oscillator. 0 = don't use OSCCAL calibration (e.g. external crystal oszillator is used). -128 = OSCCAL measure mode: the LED blinks every 60s, so the user can measure the original speed. -127..+127 = The speed is adjusted by the given amount in per mill (e.g. 10 means to speed up the device by +1%).
MinVal: -128, MaxVal: 127, Default: 0
16Reserved6 Bytesn/a
64Generic
This block contains SHC configuration data which every device has.
DeviceIDUIntValue12 BitsThe DeviceID identifies the specific unit in the SHC network. It is used to address the device and in messages the device sends. Every device has to have a different DeviceID.
MinVal: 0, MaxVal: 4095
76Reserved4 Bitsn/a
80PacketCounterUIntValue3 BytesThe PacketCounter is counted up throughout the whole lifetime of the device and is used to make the encrypted packets differently from each other every time.
MinVal: 0, MaxVal: 16777215
104Reserved19 Bytesn/a
256AesKeyByteArray32 BytesThis key is used to encrypt packets before sending and also used as primary key to decrypt packets. Special devices may have additional keys in their device specific block.
512Proxy
This block contains the specific configuration data that only Proxy devices need.
AesKeyCountUIntValue1 BytesThis is the number of AES keys to use from the AesKeys block. Limit the number to the needed amount to avoid that the base station tries decoding with every one.
MinVal: 1, MaxVal: 16, Default: 1
520AesKeyByteArray[16]32 Bytes x 16These are all AES keys which can be used to encrypt or decrypt packages at the base station.
4616TransceiverWatchdogTimeoutUIntValue1 BytesReset RFM12B module if no data is received until timeout is reached. Use this function if your specific transceiver hangs sometimes. Value is in deca seconds. Suggested setting is 48 (for 8 minutes). Set 0 to disable.
MinVal: 0, MaxVal: 255, Default: 48
4624SenderIDUIntValue[16]2 Bytes x 16These are the Sender Device IDs of the packets that shall be forwarded. Each index corresponds to the values of the following arrays with the same index. The first index with same SenderID and ReceiverID (e.g. 0) is marking from where on the entries are not considered anymore.
MinVal: 0, MaxVal: 4095, Default: 0
4880ReceiverIDUIntValue[16]2 Bytes x 16These are the Receiver Device IDs of the packets that shall be forwarded.
MinVal: 0, MaxVal: 4095, Default: 0
5136NewSenderIDUIntValue[16]2 Bytes x 16These are the (modified) Sender IDs that are used in the forwarded packets.
MinVal: 0, MaxVal: 4095, Default: 0
5392NewReceiverIDUIntValue[16]2 Bytes x 16These are the (modified) Receiver IDs that are used in the forwarded packets.
MinVal: 0, MaxVal: 4095, Default: 0
5648AesKeyNumberUIntValue[16]1 Bytes x 16These are the AES key numbers used for the (modified) forwarded packets.
MinVal: 0, MaxVal: 15, Default: 0
5776Reserved302 Bytesn/a

Hardware Overview

The proxy uses the Generic Maxi Speed PCB used as well for the base station.

Download

Assembly Instructions

Look into the Wiki for assembly instructions for the base station, which uses the same hardware.