The NanoHub transmits the power consumption measurements at 1Hz intervals.
Measurements are sent in two packets:
- Live power usage (Watt) - Cumulative energy consumption (kWh).
The hardware layer is serial UART with the following settings:
- Baud Rate : 2400bps - Character Size : 8bits - Stop Bits : 1 - Parity : None
The NanoHub uses an open collector transistor. With the following specification:
- Current sink : 10mA (max) - Vce @ 10mA : 0.7V (max)
The NanoView Display uses a 1KOhm pull up resistor with 5V source to bias the TX line.
On the Hub the pin out is as following:
1. Ground (negative) - Black 2. Power (5V - 6V) - Red 3. No Connection - Green 4. Transmit - White
Packets are tranmitted at 1Hz intervals all packets start with the start byte 0xAA followed by the packet ID byte. Then follows the DATA section of the packet. After the DATA section a two checksum bytes are sent. Multi-byte variables are sent in Little-Endian order. Accumlated Engergy counters reset to 0 (zero) each time mains power to the NanoHub is removed. The counters will increase indefinatly and wrapping is very unlikey.
* Start Byte (unsigned char): - 0xAA: Start Byte * Packet ID (unsigned char): - 0x10: Live Power Packet - 0x11: Accumulated Energy Packet - 0x12: NanoHub Firmware Version Packet * Data (array of unsigned chars): - Live Power Packet (34 bytes): -- Mains Voltage [Volts] (unsigned integer 16bits) -- 16x Live Power [Watt] (unsigned integer 16bits) - Accumulated Energy Packet (64 bytes): -- 16x Energy Counters [Watt hour] (unsigned integer 32bits) - NanoHub Firmware Version Packet (1 byte): -- Version Number (unsigned char) * Checksum (2x unsigned chars): - CRC1 (unsigned char) - CRC2 (unsigned char)
The CRC is only calculated over the Data of the packet. The pseudo code below describes the algorithm used:
crc1 = 0 crc2 = 0 for byte in data[]: crc1 = crc1 ADD byte crc2 = crc2 XOR crc1
0xAA, 0x10, 0xE6, 0x0, 0xE0, 0x2E, 0x64, 0x0, 0xC8, 0x0, 0x2C, 0x1, 0x90, 0x1, 0xF4, 0x1, 0x58, 0x2, 0xBC,
0x2, 0x20, 0x3, 0x84, 0x3, 0xE8, 0x3, 0x4C, 0x4, 0xB0, 0x4, 0x14, 0x5, 0x78, 0x5, 0xDC, 0x5, 0xFB, 0xD5
- Packet ID: : 0x10 - Voltage : 230V - Channel 1 (total) : 12000W - Channels 2 - 16 : 100W - 1500W (incrementing by 100W for each channel) - CRC1, CR2 : 0xFB, 0xD5
0xAA, 0x11, 0xC0, 0xD4, 0x1, 0x0,0xE8, 0x3, 0x0, 0x0,0xD0, 0x7, 0x0, 0x0,0xB8, 0xB, 0x0, 0x0,0xA0, 0xF,
0x0, 0x0,0x88, 0x13, 0x0, 0x0,0x70, 0x17, 0x0, 0x0,0x58, 0x1B, 0x0, 0x0,0x40, 0x1F, 0x0, 0x0,0x28, 0x23, 0x0,
0x0,0x10, 0x27, 0x0, 0x0,0xF8, 0x2A, 0x0, 0x0,0xE0, 0x2E, 0x0, 0x0,0xC8, 0x32, 0x0, 0x0,0xB0, 0x36, 0x0,
0x0,0x98, 0x3A, 0x0, 0x0, 0x21, 0x80
- Packet ID: : 0x11 - Channel 1 (total) : 120kWh - Channels 2 - 16 : 1kWh - 15kWh (incrementing by 1kWh for each channel) - CRC1, CR2 : 0x21, 0x80
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