Remote Display for Digital Caliper (24 bit serial data)
rognets
Posts: 2
Remote Display for Digital Caliper (24 bit serial data)
I am trying to build a remote display for a 'Measumax' digital caliper. The vernier caliper has a data port that I have connected too. I have identified that the displayed reading is output continually in a 24 bit binary representation. A 24 cycle clock signal is also output and corresponds to the data out. Each 24bit frame is separated by about 90 m/s space.
In each frame there are 6 sets of 4 bits (24 total) each separated by about 11.5 m/s.
Each space is about 3 m/s and a mark about 4 m/s (Inverted as GND is +tive on caliper ?)
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|This sort of represents the 00.00 reading and also the clock signal output.
The digits displayed is represented by binary. ie: -44.44 is represented by
0 0 1 1 1 0 1 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0
4 + 8 + 16 + 64 + 4096 = 4444 ( bit 21 seems to represent a negative value)
The decimal point is fixed at 2 decimal places for Metric and 3 for Imperial
HOW DO I GET THIS INTO A Basic Stamp so I can calculate and display the result
Is this what SHIFTIN is for?? Or should I use raw timing based on the above to
poll the input pin state and saved to bit variables should be fast enough?
I am hopeful that someone might have a clever way to do this????
Thanks for any help,
Steve R
I am trying to build a remote display for a 'Measumax' digital caliper. The vernier caliper has a data port that I have connected too. I have identified that the displayed reading is output continually in a 24 bit binary representation. A 24 cycle clock signal is also output and corresponds to the data out. Each 24bit frame is separated by about 90 m/s space.
In each frame there are 6 sets of 4 bits (24 total) each separated by about 11.5 m/s.
Each space is about 3 m/s and a mark about 4 m/s (Inverted as GND is +tive on caliper ?)
---_-_-_-_
_-_-_-_
_-_-_-_
_-_-_-_
_-_-_-_----_-_-_-_
|This sort of represents the 00.00 reading and also the clock signal output.
The digits displayed is represented by binary. ie: -44.44 is represented by
0 0 1 1 1 0 1 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0
4 + 8 + 16 + 64 + 4096 = 4444 ( bit 21 seems to represent a negative value)
The decimal point is fixed at 2 decimal places for Metric and 3 for Imperial
HOW DO I GET THIS INTO A Basic Stamp so I can calculate and display the result
Is this what SHIFTIN is for?? Or should I use raw timing based on the above to
poll the input pin state and saved to bit variables should be fast enough?
I am hopeful that someone might have a clever way to do this????
Thanks for any help,
Steve R
Comments
SHIFTIN is not going to work. ShiftIn and ShiftOut work with the BS2 as the master, and the other device as the slave.
To read the caliper data, the caliper is the master and the BS2 has to be the slave.
There may be a way to read it, but 3 or 4 mSec is not very much time to do much on the BS2.
Bean.
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I think what You have is a 24 bit WORD and your seeing a bunch of glitches. I could be wrong. If this is a cheap Chinese scale,Than I'm more than likely dead on the money. If it is a Chinese scale here is some data I have on them.
There is two 24bit words sent out L.S.B. first @ around 77kHz
The 1st 24bit word is the absolute position
The 2nd 24bit word is the relative position
This is around 1.77 volts peak above Vss, since it runs off of a SR77 watch batt.
Check out ShumaTech.com for more info
Again this may not be what you have
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I am looking at the data straight from the caliper not the serial converted data.
Steve R