Experimental Physics and
Industrial Control System

"Zimoch Dirk \(PSI\) via Tech-talk" <tech-talk at aps.anl.gov> · Thu, 11 Nov 2021 08:28:43 +0000

.. or isn't this the string "A1 61 00 00 00 05 DC 02 58 00 11 00 0D" but really only the byte squence?

In that case:
I do not have a bitsum yet. But if I had, it would look like:

terminator = 0x0d;
set_A_AND_I {
    out 0xa1 0x61 0x00 0x00 0x00 "%2r%(\$1:CURRENT)2r%<bitsum>";
    in  0xa1 0x0a 0x00 0x00 0x00 "%=2r%(\$1:CURRENT)=2r%<bitsum>";
}

I use redirection for the second value (current) while taking the first (voltage) from the active record. The reply is
checked for correctness with %= against the current settings. (I hope I understood this right.)

On Thu, 2021-11-11 at 08:13 +0000, Zimoch Dirk (PSI) via Tech-talk wrote:
> Hi Josh,
> 
> StreamDevice cannot do this "double encoding" at the moment. I have seen this request several times but do not have a
> solution yet. One may implement an asynInterpose layer which converts between the string
> "A1 61 00 00 00 05 DC 02 58 00 11 00 0D"
> and the byte sequence
> 0xA1 0x61 0x00 0x00 0x00 0x05 0xDC 0x02 0x58 0x00 0x11 0x00 0x0D
> 
> Then StreamDevice can work on the byte sequence and can convert between the two byte sequence 0x05 0xDC and the
> integer
> 0x05dc=1500 and scale it to 15.00.
> 
> But first converting between 15.00 and 0x05 0xDC and then again to "05 DC" is beyond what StreamDevice can do alone.
> 
> Dirk
> 
> 
> On Wed, 2021-11-10 at 16:20 -0500, Josh Fiddler via Tech-talk wrote:
> > Hi EPICS mavens!
> > 
> > I'm having a lot of fun building IOCs left and right. 
> > 
> > Here are some important details:
> > 
> > I've got a HV power supply to charge up a system that comms over RS485. 
> > We send 13 bytes worth of data to the unit, including 2 bytes for the terminator.
> > byte are
> > 1 for address, 
> > 2 for command
> > 2 used as header in certain commands: to hold status bytes in some, and is null in others
> > 2 when we want to set a voltage
> > 2 when we want to set the ramping current
> > 2 for checksum
> > 2 for terminator
> > 
> > To pass a voltage, it must first be in tens of kV, sensitive to 0.1 kV. This value is multiplied by 100 then can be
> > converted to hex. Current is similar, but is not scaled (x1) 
> > 
> > The checksum is the sum of the bits in the binary representation of the first 9 bytes. When I send the request, I
> > must
> > include this value. It is to ensure the message is composed of characters, according to the docs (which are very,
> > very
> > minimal). 
> > 
> > So, an example command to set the device to 15kV, with 600mA current is:
> > 
> > A1 61 00 00 00 05 DC 02 58 00 11 00 0D
> > where 05 DC represents 15kV (hex(15 * 100))
> > and    02 58 represents 600mA (hex(600))
> > and    00 11 represents checksum on A1 61 00 00 00 05 DC 02 58
> > The checksum is computed by summing the individual bits in the binary of each value: 
> > 0b10100001', '0b1100001', '0b0', '0b0', '0b0', '0b101', '0b11011100', '0b10', '0b1011000' 
> > means 3+3+0+0+0+2+5+1+3=17 or 0x11 in hex. 
> > 
> > When we receive responses from the PS, it has the same structure as the request. The second 'Command' bytes is
> > modified to 0x0A. The rest of the bytes are unique to the request. 
> > 
> > We can request the 'parameters' that are currently set by calling
> > 
> > A1 63 00 00 00 00 00 00 00 00 07 00 0D where the checksum is 0x0007
> > since A1->3, 63->4 and 7 in hex is 0x07. 
> > 
> > The response would contain the same first 2 bytes, with the 3rd now 0A to show is a response. In the parameter
> > response, the 4th and 5th bytes represent the system state when each is converted to a binary representation, and
> > each
> > bit indicates some status. 
> > 
> > The ask:
> > 
> > How can I extract this information and use it?  Should I use record redirection to put the values and formatters? 
> > 
> > Could someone point me in the right direction? 
> > 
> > Thanks for reading. 
> > 
> > I also have another question here that I could use some help with 
> > Search: "StreamDevice checksum Methods"

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System