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shirriff / tan.py
Created May 14, 2020 01:04
Demo of the 8087's CORDIC tangent algorithm
import math
# 8087 tangent algorithm, from Implementing Transcendental Functions, R. Nave
atan_table = [math.atan(2 ** -i) for i in range(0, 17)]
def cordic_tan(z):
# Compute tan of angle z, using CORDIC
q = []
# Break down z into sum of angles, where each angle is 0 or atan(2**-i)
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shirriff / main.c
Last active March 16, 2024 13:51
Example code using a timer with the BeagleBone Black's PRU microcontroller. This code generates 5 pulses with 100ns width.
/*
* Demonstration of the BeagleBone's PRU, using a timer.
* Ken Shirriff, http://righto.com
*/
#include <stdint.h>
#define DELAY_NS 100 // Use 500000000 for 0.5 second delay
#define WRITE_PIN 15 /* P8_11, Ethernet output data, pr1_PRU0_pru_r30_15 */
// PRU Interrupt control registers
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shirriff / edid.py
Created March 25, 2018 15:58
Parse VGA configuration data (EDID) accessed from I2C device 0x50
# Program to parse VGA data (EDID) accessed from I2C device 0x50
#
# This is a quick demo not a supported program, so don't expect
# correctness from it.
#
# Edid format from:
# https://en.wikipedia.org/wiki/Extended_Display_Identification_Data#EDID_1.4_data_format
#
# Ken Shirriff http://righto.com
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shirriff / days-in-month
Last active October 24, 2022 14:22
HP Nanoprocessor code to determine the number of days in a month
d0 STR-0 Store the next byte (7) in register 0.
07
0c SLE Skip two instructions if accumulator <= register 0.
03 DED Decrement the accumulator in decimal mode
5f NOP No operation
d0 STR-0 Store the next byte (0x31) in register 0
31
30 SBZ-0 Skip two instruction bytes if accumulator bit 0 is zero
81 JMP-1 Jump to 0x1c9 (end of this code block)
c9
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shirriff / notes.py
Last active December 23, 2021 21:13
UM66T sound chip analysis program
# This code prints out the melody in the UM66T sound chip's ROM.
# The ROM holds Jingle Bells, Santa Claus is Coming to Town, and We Wish You a Merry Christmas.
# See this Twitter thread for details: https://twitter.com/kenshirriff/status/1472297415201869831
from collections import defaultdict
notes = ['X', 'X', 'G4', 'A5', 'B5', 'C5', 'D5', 'E5', 'F5', 'G5', 'A6', 'B6', 'C6', 'X', 'X', 'X']
# Hard-coded ROM contents.
bits = {"24,1":0,"15,0":1,"15,1":0,"15,3":1,"15,4":0,"14,4":1,"13,4":0,"12,4":1,"11,4":0,"10,4":1,"9,4":1,"8,4":0,"7,4":0,"6,4":1,"5,4":1,"4,4":0,"0,4":0,"1,4":1,"2,4":1,"3,4":0,"0,1":1,"0,0":1,"3,0":1,"4,0":1,"7,0":1,"8,0":1,"11,0":1,"12,0":1,"17,0":1,"19,0":1,"20,0":1,"23,0":1,"25,0":1,"26,0":1,"29,0":1,"31,0":1,"30,1":1,"28,1":1,"26,1":1,"25,1":1,"22,1":1,"21,1":1,"18,1":1,"17,1":1,"30,5":1,"31,6":1,"30,8":1,"30,9":1,"30,10":1,"31,11":1,"31,13":1,"31,14":1,"30,15":1,"31,16":1,"30,18":1,"30,19":1,"31,20":1,"31,21":1,"30,23":1,"31,24":1,"31,25":1,"31,26":1,"31,28":1,"30,29":1,"30,28":0,"29,
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shirriff / analyze-IR-signal.py
Created July 18, 2013 06:48
#!/usr/bin/python
""" Download an IR remote signal from a Rigol DS1052E and
analyze it for a NEC protocol signal.
Ken Shirriff
http://righto.com
"""
import array
import sys
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shirriff / password.c
Created January 4, 2018 02:33
Use brute force to crack the password on a Xerox Alto disk.
#include <stdint.h>
#include <stdlib.h>
#include <strings.h>
#include <stdio.h>
int64_t count = 0;
// Password vector from sys.boot. Must be big-endian.
// Disk 47
uint16_t passvec[] = {0xffff, 0xcfa7, 0x9f3d, 0x669a, 0xf2bb, 0xf193, 0x6d09, 0x4571, 0xe1d1};
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shirriff / music_1401.txt
Created September 7, 2019 21:24
Music program for the IBM 1401, along with frequency cards. Courtesy of Ron Mak.
,008015,022033L067135,1050291001/099H104C104135B101/,0011/001199199 0001MUSIC
,109116,121125,126133/101099 0002MUSIC
,008015,022029,036040,047054,061068,072/061039 ,00100110400003MUSIC
0000000000000,001/000H099L/49089 L032118,092097,100104,10811210400004MUSIC
L/490941C003/53B334SM0996J5B165DL/54354L039157,126127,134139,14615110400005MUSIC
M0756J1A/56094M0660?0H0991L0660?0H099 L037194,165172,179183,18419110400006MUSIC
A/57089C089/59B126U.100 L023217,202209,214040,04004010400007MUSIC
M585099/332/,0052011N372M002005 L031364,341345,346353,35435810400008MUSIC
M/60002B564001XB353001 B503001RL/49089 L038402,372380,388396,04004010400009MUSIC
C0036/1B438SA/56089C089094B403U.100 L035437,410415,422429,43404010400010MUSIC
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shirriff / music-1403.txt
Created September 2, 2019 16:21
Disassembly of a vintage program to generate music on an IBM 1403 line printer.
87 00000 # X0
92 00000 # X1
97 000 # X2
100 ,001 set wordmark 1 # Start
104 /000 clear storage 0 # Wraps to top of memory?
108 H099 store B* 99 # Top of memory - 100? into X2
112 L/49089 load 1149 89 # X1 = 0
119 L/49094 load 1149 94 # X2 = 0
126 1 read # READNOTE: Read first card
127 C003/53 compare 3 1153 # Card has END?
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shirriff / blink.p
Last active May 15, 2019 12:58
Assembly code to demonstrate the PRU on the BeagleBone Black. This code blinks an LED 10 times.