Embedded Files
Ok, next lets us add the ability to measure 3 channels of interferometer data at once.
In order to do that we will change the pin assignments slightly again, moving MEAS1 from pin 7/RB14 to pin 11/RB0.
Also, neither of those two pins are 5V tolerant, so what should have been done for version 1.1 already is a resistor divider to handle that. We will use 400/1000 Ohm resistors for this purpose.
Note that the resistor color codes do no reflect the actual values.
We are at (probably past) the point where the routing on the picture is useful, and a schematic is more appropriate. But for completeness, here is the picture with the additional hardware to complete the 3 axis interferometer:
The final pin and PIC hardware layout with respect to the counters, then is:
Input Counter TxCKR Bus Address Pin Signal Notes
------------------------------------------------------------------ REF Timer3 0b0001 0xbf800A10 0/RB5 RPB5 MEAS1 Timer5 0b0010 0xbf800E10 11/RB0 RPB0 LED4 MEAS2 Timer4 0b0100 0xbf800C10 13/RB2 RPB2 LED2 MEAS3 Timer2 0b0001 0xbf800810 14/RB3 RPB3 LED1The bus address is important because reading the timers is timing critical. So I am doing that with in-line assembly code.The more general pin assignment is this: Usage Pin (Arduino/PIC) Notes ------------------------------------------------------------------ REF 0/RB5 AM2303 1/RB7 BMP180 2/RB8 BMP180 3/RB9 USB+ 4/RB10 USB- 5/RB11 6/RB13 7/RB14 8/RB15 9/RA0 10/RA1 MEAS1 11/RB0 LED4 12/RB1 LED3 MEAS2 13/RB2 LED2 MEAS3 14/RB3 LED1 CLOCK 15/RA2 16/RA3 17/RB4 18/RA4That permits the DP32 board to measure 3 channels of interferometer data as well as two independent temperature measurements as well as humidity and air pressure.
Here is the SAR file with the firmware: https://sites.google.com/site/janbeck/Interferometer_3axis.sar
Sam Goldwasser maintains a separate firmware, using identical pinouts and communications protocol.
You can find that firmware (and a great Installation and Operation Manual) here:
http://repairfaq.cis.upenn.edu/Misc/uMD1/uMD1.htm
Eventually, the difference between the firmwares should just be performance. But for now, Sams firmware does phase estimation while mine does not yet do that.
And the GUI, which should work with any of the firmwares is available here:
https://github.com/janbbeck/InterferometerGUI
Here is the expanded message format for 3 axis data, including environmental data:
Standard (Single Axis) Data (8 values):
0: REF Frequency Count = REF frequency/610.35
1: MEAS Frequency Count 1 = MEAS 1 frequency/610.35
2: Displacement 1 ( in 1/2, 1/4, or 1/8 wavelength)
3: Velocity Count 1 = (Displacement 1 - Previous Displacement 1)/610.35
4: Phase 1 = Fractional offset between Displacement increments * 256 If Phase is not valid, then an error code is sent instead: 0x4000=no PORTB MEAS 1 0x2000=no PORTB 2nd REF 0x1000=no PORTB 1st REF 0x800=no Timer3/5 MEAS 1 0x400=no Timer3/5 2nd REF 0x200=no Timer3/5 1st REF
5: Sequence Number (Unique serial number for each sample)
6: LowSpeedCode (See below)
7: LowSpeedData (see below)
The following 8 values will also be sent when Multiple Axis Mode is active:
8: MEAS Frequency Count 2
9: Displacement 2
10: Velocity Count 2
11: Phase 2
12: MEAS Frequency Count 3
13: Displacement 3
14: Velocity Count 3
15: Phase 3 LowSpeedCode (specifies contents of LowSpeedData): 0-99: GUI Data/Control: 0: No Data 1: Laser Power 2: Signal Strength 3: Temperature 1 ( in percent, so 2345 is 23.45 degrees) 4: Temperature 2 ( in percent, so 2345 is 23.45 degrees) 5: Pressure ( in pascal ) 6: Humidity ( in tens of percent, so 234 is 23.4 percent humidity) 7: Data Source ID
20: Homodyne interferometer if non-zero
(Not all of these are currently implemented.) 100-199: Diagnostics 200-255: Reserved
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