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Need RS 232 help.
This thread has 5 replies. Displaying all posts.
Post 1 made on Friday December 4, 2009 at 05:53
danieljgor
Long Time Member
Joined:
Posts:
December 2008
105
Hi Guy's

I have Played with alot od Ascii RS232 devices, but cannot make sense of my Everfocus DVR.

For instance REC to DVD with id 5

0x85 (length)
0x00 (receiver id high byte)
0x05 (receiver id low byte)
0x4B (OPcodekey)
0x08 (Data key = rec)
0x5d (checksum)



Play Code is 0B so is bellow correct or will check sum change?

0x85 (length)
0x00 (receiver id high byte)
0x05 (receiver id low byte)
0x4B (OPcodekey)
0x0B (Data key = Play)
0x5d (checksum)


Now if i put this into my pronto as a hex code i cant seem to get it to work. below is and example for record inputed into pronto
85 00 01 4B 08 5d

Do i need to work out a check sum? i have tried for hours...

Please help.


Thanks
Daniel
Post 2 made on Saturday December 5, 2009 at 09:27
stjoh
Long Time Member
Joined:
Posts:
April 2009
16
Checksum is typically calculated based on the command so most likely you'll have to create a new one for each command.
OP | Post 3 made on Monday December 7, 2009 at 02:02
danieljgor
Long Time Member
Joined:
Posts:
December 2008
105
Hi Stjoh,

is there a program to create these individual check sums? as i have no idea on the way to calculate them.

Thanks
Daniel
Post 4 made on Monday December 7, 2009 at 07:44
mark65
Long Time Member
Joined:
Posts:
November 2003
450
Which model of everfocus are you using?
OP | Post 5 made on Monday December 14, 2009 at 15:19
danieljgor
Long Time Member
Joined:
Posts:
December 2008
105
Hi Mate,

EDR410M

Thanks Daniel
Post 6 made on Monday December 14, 2009 at 18:28
mark65
Long Time Member
Joined:
Posts:
November 2003
450
Here is a different example from the manual. For better results we will use the broadcast ID. This way it doesn't matter what ID the DVR is set to.

0x85 (length) (This will always be 85)
0x7f (Receiver ID high byte) (This will always be 7F)
0x7f (Receiver ID low byte) (This will always be 7F)
0x4B (OPcode = key ) (This will always be 4B)
0x0B (DATA1 = "Play" keycode ) (This is the DATA from page 144)
0x59 (checksum) (Sum of all bytes AND 7F)

To calculate the checksum I suggest using Windows calculator in Scientific mode:
1. Add the first five bytes together.
2. If the sum is a 3 digit number, delete the left-most digit.
3. Using the AND operation on the calculator AND the sum with 7F.

So from the above example:
85+7F+7F+4B+0B= 1D9
We delete the left-most bit and our sum= D9.
D9 AND 7F= 59 (This is the checksum)

Our final string is then:
85 7f 7f 4b 0b 59

Here is the string for CH3
85 7f 7f 4b 02 50

Hope this helps.


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