Re: Re: Re: The problem of converting floating-point numbers to 4-byte format (in CDAB order) under StreamDevice

[高振华 via Tech-talk <tech-talk at aps.anl.gov>]

OK, I see. Thanks a lot, Dirk.

Gao Zhenhua


> -----原始邮件-----
> 发件人: "Zimoch, Dirk" <dirk.zimoch at psi.ch>
> 发送时间:2026-01-08 20:40:19 (星期四)
> 收件人: "gaozh at ihep.ac.cn" <gaozh at ihep.ac.cn>
> 抄送: "tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov>
> 主题: Re: Re: The problem of converting floating-point numbers to 4-byte format (in CDAB order) under StreamDevice
> 
> On Thu, 2026-01-08 at 13:38 +0100, Zimoch Dirk wrote:
> > Only big endian order (ABCD) or little endian (DCBA) but no mixed endian (CDBA
> > or BACD).
> 
> I mean: no mixed (CDAB or BADC).
> 
> > 
> > 
> > On Thu, 2026-01-08 at 20:09 +0800, 高振华 wrote:
> > > Hi Dirk,
> > > Could "%#.4R" convert the 4-byte value 40 49 99 9A (in hexadecimal, big-endian order, ABCD order) corresponding to 3.15 into 99 9A 40 49 (in CDAB order)?
> > > 
> > > Thanks,
> > > 
> > > Gao Zhenhua
> > > 
> > > > -----原始邮件-----
> > > > 发件人: "Zimoch, Dirk" <dirk.zimoch at psi.ch>
> > > > 发送时间:2026-01-08 16:33:27 (星期四)
> > > > 收件人: "gaozh at ihep.ac.cn" <gaozh at ihep.ac.cn>, "tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov>
> > > > 主题: Re: The problem of converting floating-point numbers to 4-byte format (in CDAB order) under StreamDevice
> > > > 
> > > > Hi Gao
> > > > 
> > > > As Mark already wrote, better use the dedicated Modbus driver, but for
> > > > completeness here is the answer: Use format "%.4R"
> > > > 
> > > > %R is the "floating point raw" format and can be used with precision .4 or .8
> > > > for float or double. By default it used big endian byte order but if needed that
> > > > can be changed to little endian with "%#.4R".
> > > > https://urldefense.us/v3/__https://paulscherrerinstitute.github.io/StreamDevice/formats.html*rawdouble__;Iw!!G_uCfscf7eWS!e6Db1wUpZwLKEdt4Sf3GvbfQpETHTiAVjjTZu-3NmFgaMIYYBco4kIE8w8TlHedTV2ZRuI5H7b2zA8mqLYBa$ 
> > > > 
> > > > BTW: The Modbus checksum is "%<modbus>".
> > > > https://urldefense.us/v3/__https://paulscherrerinstitute.github.io/StreamDevice/formats.html*chksum__;Iw!!G_uCfscf7eWS!e6Db1wUpZwLKEdt4Sf3GvbfQpETHTiAVjjTZu-3NmFgaMIYYBco4kIE8w8TlHedTV2ZRuI5H7b2zA22IV1pO$ 
> > > > 
> > > > 
> > > > Dirk
> > > > 
> > > > On Wed, 2026-01-07 at 17:53 +0800, 高振华 via Tech-talk wrote:
> > > > > Hi all,
> > > > > 
> > > > > 
> > > > > 
> > > > > I am conducting Modbus RTU communication with a device and need to convert a 32-bit floating-point number into 4 bytes of hexadecimal data and then send it to the device.
> > > > > 
> > > > > For example: 3.15 converted to 4 bytes is 40 49 99 9A (in hexadecimal, big-endian order, ABCD order).
> > > > > 
> > > > > Using StreamDevice, how should I convert to the CDAB order? (For example, the CDAB order corresponding to 3.15 is 99 9A 40 49).
> > > > > 
> > > > > Does StreamDevice have a corresponding conversion symbol?
> > > > > 
> > > > > 
> > > > > 
> > > > > 
> > > > > Best regards，
> > > > > 
> > > > > 
> > > > > Gao Zhenhua
> > > > > 
> > > > > 
> > > > > BSRF
> > > > > 
> > > > > Email:gaozh at ihep.ac.cn
> > > > > 
> > > > > 
> > > 
> > > ------------------------------
> > >       
> > > 祝好！
> > > 高振华
> > > 
> > > 电话：010-88235426
> > > Email:gaozh at ihep.ac.cn
> > >


------------------------------
      
祝好！
高振华

电话：010-88235426
Email:gaozh at ihep.ac.cn