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-------------------------------------------------------------------------------
MAX6921 Shift Register
-------------------------------------------------------------------------------
This is a capture of data output to a Maxim MAX6921 high voltage shift
register that was outputting data for a VFD clock.
The signals were grabbed on a 28-pin PLCC chip (MAX6921) which outputs 20-bits
that is crafted as a design for VFD applications.
Details:
- BeagleBoard.org vendor tree: https://github.com/beagleboard/kernel
- Beagle Nixie GitHub: https://github.com/mranostay/beagle-nixie/
- MAX6921 datasheet: http://datasheets.maximintegrated.com/en/ds/MAX6921-MAX6931.pdf
Logic analyzer setup
--------------------
The logic analyzer used was Open Bench Logic Sniffer (at 10MHz):
Probe MAX6921 pin
--------------------------
0 LOAD
1 DATA
2 CLK
3 BLANK (PWM Brightness Control)
Data
----
The data contain various values for the VFD being driven, as reference at the
prototype Nixie Cape for the Beaglebone.
Digit Bit
-----------------------
0 (1 << 12)
1 (1 << 19)
2 (1 << 13)
3 (1 << 18)
4 (1 << 14)
5 (1 << 17)
6 (1 << 16)
7 (1 << 15)
8 (1 << 15)
9 (1 << 11)
Segment Bit
-----------------------
SEG_A (1 << 0)
SEG_B (1 << 1)
SEG_C (1 << 2)
SEG_D (1 << 3)
SEG_E (1 << 4)
SEG_F (1 << 5)
SEG_G (1 << 6)
SEG_H (1 << 7)
The sigrok command line used was:
sigrok-cli --driver=ols:conn=/dev/ttyACM0 --config samplerate=10mhz \
--samples=24576 -p 0=LOAD,1=DATA,2=CLK,3=BLANK -o <filename>
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