Open2300 - Open WSAPI

Interface / API Description for WS-23XX

This document is unofficial and contains information that owners of the WS-23XX have collected by experiments.

The purpose of this document is to help the owner using the product under Linux to write their own interface program for the Weather station.

This site is not associated with the manufacturer in any way. There is no guarantee of the correctness of the information in this document and the use of the information is at your own risk. The author cannot be held responsible for any damage use of this information may cause.

The weather station actually does not really have an API. It has a few commands to read and write to the memory of the weather station. All the data you collect from the weather station is simply raw data fetched from the memory.

This topic describes the physical RS232 interface and how to read and write data to and from the weather station.

Serial Port Settings.

Baudrate 2400 Bits 8 Parity None Stopbits 1

Physical connection

RS232 Wire Colour Function
Pin 2 RXD Orange wire Receive data from WS2300
Pin 3 TXD Green wire Transmit data to WS2300
Pin 4 DTR White wire Signal from PC to WS2300
Pin 7 RTS Blue wire Signal from PC to WS2300
Note:

There is no ground connection.

DTR and RTS are not used for handshake. They are steady DTR at negative voltage and RTS at positive voltage.

Since there is no ground it seems that the WS2300 uses the DTR and RTS to define high and low. DTR must be low and RTS must be high for the communication to work.

Some USB-Serial adapters do not support DTR and RTS. If your WS2300 does not communicate, check the voltage of DTR and RTS at the connector.

(My Ethernet/Serial converter Lantronix MSS-100 doesn't allow user to control DTR/RTS wires and both signals were high (+12V) all the time. There was no wire with low (-12V) on connector. So I tried to connect DTR directly to GND... and it works.)

Basic Protocol

The communication with the WS-2300 is very primitive. There is no real user interface. The only thing you can do is read and write from the memory of the device. The device seems to have a memory area of around 5k. Memory area starts at 0000 and ends around 13C0.

Most data except alarm flags are in the range 200-6C5. History records starts from 6C6. Each record is 19 bytes.

Commands are normally sent 1 byte at a time and one byte is returned as a receipt.

The initial command is 0x06, which signals the WS2300 to start all over with same data as before.

Twice 0x06 without a read between seems to mean rewind to initial data.

Except for the 0x06 commands are always 5 bytes.

Errors

When reading and writing to the WS 2300 the communication often fails. The station simply does not see RS232 communication as first priority and refuses to answer when it does something else. Errors happen quite often.

When you get no answer or a wrong check byte returned start again by sending 06. You should now get the answer 02 back. If not, repeat sending 06 until you receive 02 and then the entire command all over again.

Reading

  • First 4 bytes is the first nibble address to read from. Note that addresses are in nibbles even though you read in bytes.
  • The address is a 13 bit number which can be seen as 4 hexdigits (4-bit nibbles) (First digit is either 0 or 1).
  • The address is coded as hexdigit*4+0x82.
  • WS2300 returns 0S, 1S, 2S and 3S where S is a check digit calculated as (command-0x82)/4. I.e. S is the hex digits of the address.
A more graphical way to see it is like this.

1 0 0 0 0 0 1 0 0x82
+  
0 0 A3 A2 A1 A0 0 0 Address * 4
=  
1 0 A3 A2 A1 A0 1 0 Command

Here is a table that translate between hex digit and command.

Command Hex Digit   Command Hex Digit
82 0   A2 8
86 1   A6 9
8A 2   AA A
8E 3   AE B
92 4   B2 C
96 5   B6 D
9A 6   BA E
9E 7   BE F

When reading data the last byte is the number of databytes requested. It is coded as number*4 + 0xC2. See table below. Max value is 15.

1 1 0 0 0 0 1 0 0xC2
+  
0 0 N3 N2 N1 N0 0 0 Number * 4
=  
1 1 N3 N2 N1 N0 1 0 Command

Here is a table that translate between number and command.

Command Number   Command Number
C6 1   E6 9
CA 2   EA 10
CE 3   EE 11
D2 4   F2 12
D6 5   F6 13
DA 6   FA 14
DE 7   FE 15
E2 8      

WS2300 returns 3X where X is the number of data bytes to follow (excluding the checksum byte). The first byte 3 is some fixed header.

Data bytes are now all sent at once.

Finally, a checksum is sent which is the low byte of the sum of the databytes sent.

Writing 4-bit Nibbles

When writing you set up the address the same way as when reading.

To write a nibble (4-bits) the data write command byte is calculated as (data_nibble*4)+0x42.

0 1 0 0 0 0 1 0 0x42
+  
0 0 D3 D2 D1 D0 0 0 Data * 4
=  
0 1 D3 D2 D1 D0 1 0 Command

Here is a table that translate between number and command.

Command Hex Digit   Command Hex Digit
42 0   62 8
46 1   66 9
4A 2   6A A
4E 3   6E B
52 4   72 C
56 5   76 D
5A 6   7A E
5E 7   7E F

The station will acknowledge every written nibble write command by returning (0x10 + hexdigit).

0 0 0 1 D3 D2 D1 D0 Ackowledge Data

After the last data byte is written you send can either send 06 init command (acknowledged by 0x02) or a new read/write address (0x82/0x83) which is then acknowledged by 0x00/0x01. It is probably a good idea to end the writing in some controlled way so that no more data is written to the station accidentally.

Writing 1-bits

Same method as for writing nibbles except data commands have the following format. Command for setting a bit (numbered from 0 to 3) is (bit_no*4)+0x12 and the acknowledge is 0x04+bit_no. Command for resetting a bit is (bit_no*4)+0x32 and the acknowledge is 0x0C+bit_no. Setting a bit

0 0 0 1 0 0 1 0 0x12
+  
0 0 0 0 B1 B0 0 0 Bit Number * 4
=  
0 0 0 1 B1 B0 1 0 Command

Acknowlegde setting bit

0 0 0 0 0 1 B1 B0 Ackowledge Data

Resetting a bit

0 0 1 1 0 0 1 0 0x32
+  
0 0 0 0 B1 B0 0 0 Bit Number * 4
=  
0 0 1 1 B1 B0 1 0 Command

Acknowledge resetting bit

0 0 0 0 1 1 B1 B0 Ackowledge Data

-- KennethLavrsen - 02 Jul 2005
Topic revision: r5 - 04 Apr 2011, PetrBrouzda
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