S7-300 标签数据写入异常，使用 write_tag 方法。

[b1163646804]

1、版本：python-snap7
2、执行数据写入：
成功√：client.write_tag("DB1600:34:STRING[10]", "HELLO C")
错误×：client.write_tag("DB1600:34:STRING[10]", "你好")
3、错误日志：

Traceback (most recent call last):
  File "E:\works\hcserverex\utils\s7_utils\demo_s7.py", line 26, in <module>
    main()
  File "E:\works\hcserverex\utils\s7_utils\demo_s7.py", line 20, in main
    client.write_tag("DB1600:34:STRING[10]", "你好")
  File "E:\works\hcserverex\venv\Lib\site-packages\snap7\client.py", line 831, in write_tag
    _encode_tag(resolved, buf, value)
  File "E:\works\hcserverex\venv\Lib\site-packages\snap7\client.py", line 142, in _encode_tag
    util.set_string(buf, 0, value, length)
  File "E:\works\hcserverex\venv\Lib\site-packages\snap7\util\setters.py", line 229, in set_string
    raise ValueError(
ValueError: Value contains ascii values > 255, which is not compatible with PLC Type STRING. Check encoding of value or try set_wstring().

[gijzelaerr]

This is the write side of the same issue as #786 — the STRING encoding path does not handle multi-byte characters.

Already fixed in PR #788 (branch fix/786-multibyte-string-encoding). With that branch, you can write Chinese strings like this:

client.write_tag("DB1600:34:STRING[10]", "你好", encoding="gbk")

You can test now with:

pip install "python-snap7 @ git+https://github.com/gijzelaerr/python-snap7.git@fix/786-multibyte-string-encoding"

Closing as duplicate of #786.

[gijzelaerr]

Duplicate of #786, fixed in #788.

[b1163646804]

@gijzelaerr Hi.

测试 S7-300 PLC 如下：

我的Demo1 Code：

from snap7 import Client

client = Client()
client.set_connection_type(connection_type=2)
client.connect("192.168.0.102", 0, 2)
client.write_tag("DB1600:34:STRING[10]", "明天，您好", encoding="gbk")
text = client.read_tag("DB1600:34:STRING[10]", encoding="gbk")
print(text)

结果： "明天，您好" 可以正常写入，以及输出正常。

测试 S7-200 smart PLC 如下：

我的Demo2 Code：

from snap7 import Client

client = Client()
client.set_connection_type(connection_type=2)
client.connect("192.168.0.101", 0, 1)
client.write_tag("DB1:11:FSTRING[8]", "您好", encoding="gbk")
text = client.read_tag("DB1:11:FSTRING[8]", encoding="gbk")
print(text)

结果： "您好" 可以正常写入，以及输出正常。

[gijzelaerr]

@b1163646804 Great — confirmed working on both S7-300 and S7-200 Smart with encoding="gbk" for read and write. Thanks for testing!

This is fixed in PR #788.