protocol.txt

DIY Kyoto Wattson serial protocol - http://www.diykyoto.com/

Mikko Pikarinen, 23.1.2011

NOTE: The protocol has been found out by reverse engineering, so this 
document is not complete and it may contain errors.


The DIY Kyoto Wattson power meter acts as a USB serial converter, so one 
can communicate with it like with any serial device. The settings for 
serial port are 19200,8N1.
Linux lsusb tells:
ID 0403:6001 Future Technology Devices International, 
             Ltd FT232 USB-Serial (UART) IC

The protocol consists from one line commands and responses. Every 
command begins with characters "now" and is followed by one char for 
command and with some commands extra parameters. If the command char is 
in upper case, it means write eg. when syncing the clock. A command ends 
always with carriage return \r (ascii 13). The response begins with the 
command letter and ends with two carriage returns. Eg. command "nowd\r" 
is for asking the count of stored days and the response may be eg. 
"d02\r\r".

DANGER: some commands (eg. "nowo") may brick the device, and it must be 
reset by removing the battery.

The known commands are:

  nowa - Possibly the long time average watts in dec. Not confirmed.
  nowd - Get number of days of data stored except the day going on.
          The response is "dNN" where NN is stored days count.
  nowe - Erase all stored power data except the current day from unit.
         It may be needed that this command is sent as "nowE"
  nowl - Get stored power readings. See below.
  nowp - Get current power usage 
          The response is "pXXXX" where XXXX is watts in hex
  nowr - Possibly the stored elecricity price rates
  nows - Get unit serial number
          The response is "sNNNNNN" where NNNNNN is dec numerals
  nowt - Get/set unit date/time (setting may need nowT)
          The format is: "YY/mm/dd HH:MM:SS"
          eg. "nowT11/01/23 13:37:00" is confirmed to work.
  nowv - Possibly the firmware version. My unit says "vW010701CLK"
  noww - According to the DIY Kyoto helpdesk this is the command to get
         the value for the power being generated currently (Wattson Solar Plus model). 

Some other commands (b,c,f,g,i,j,k,q,w,x) work too, but they give 
responses of 1-12 numbers that don't ever change and I haven't guessed 
what they mean. The command "nowy" answers always just "y".

The nowl command:

The "nowl"-command is for downloading the stored power averages. Wattson 
stores average power usage every 5 minutes. The values are stored in day 
slots which all are divided to 12 two-hour slots.

The number of stored days can be retrieved by command "nowd". The response
is stored days count eg. "d02" if two days before today has been stored.
The oldest dayslot is 01, the next 02 etc. so todayÃ's slot is the response
from nowd command +1. In the example "d02" today is slot 03.

Every day contains 12 two-hour slots as said before. The first slot for 
hours 00 and 01 is "01" and therefore slot for 8pm to 10pm is 11. 

The format for command "nowl" contains always the dayslot and the 
hourslot. Eg. if you want to download the first 2-hour slot for today 
and you got "d02" from the "nowd" command, send "nowl0301". The response 
is one line beginning with letter "l" and containing 5min averages in 
watts in hexadecimal, fields separated by commas and in the end there is 
a 2-byte checksum and of course the carriage return. I haven't tried to
find out the algorithm for the checksum.

The row may be eg: (it is not really wrapped, it is one 123 byte line)

l164A,1231,1436,1525,1781,1BEA,16B0,15DD,10E1,10C8,115F,1386,1472,
12B0,1072,12E2,16D3,115F,141B,FFFE,FFFF,FFFF,FFFF,FFFF,CC

The current 5min timeslot contains "FFFE" and the timeslots which are in 
the future contain "FFFF". From this slot you see, that in the first 5 
minutes of that time the average power usage was 0x164A watts which is 
5706 W in decimal.