From 7aeaed651f1c2e2ee1dd8923f2ffd22e2bd5e34c Mon Sep 17 00:00:00 2001
From: John-Mark Gurney <jmg@funkthat.com>
Date: Fri, 5 Aug 2022 16:51:05 -0700
Subject: [PATCH] add code that does binary to three level + clock recovery...

This is sample code, but works well.. it ensures that every bit
time there is a level change, so any duplicates can be dropped..

this works so far, but I'm sure is not the most effecient way to
do this...
---
 blinkled/genseq.py | 78 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 78 insertions(+)

diff --git a/blinkled/genseq.py b/blinkled/genseq.py
index 0295bdc..40266c3 100644
--- a/blinkled/genseq.py
+++ b/blinkled/genseq.py
@@ -1,3 +1,81 @@
 from encdec8b10b import EncDec8B10B
 
+a = b'Hello, this is a test of encoding.'
+
+coder = EncDec8B10B()
+
+encoded = coder.encode(EncDec8B10B.COMMA) + coder.encode(a)
+print('8b10b encoded:', repr(encoded))
+
+decoder = EncDec8B10B()
+
+print(repr(decoder.decode(encoded)))
+print('test decode:', repr(decoder.decode('')))
+
+def jm3coder(bits, lastlvl=0):
+	'''Takes in a string of bits, and outputs a trinary level.
+	It is guaranteed that no two outputs repeat allowing for
+	easy clock recovery as long as the sampling rate is faster
+	than output rate.  (e.g. 30Hz (33.3ms) sampling of a 29Hz
+	(34.5ms) signal.
+
+	Note that this does not do sync, so something like an 8b10b
+	encoder should be used on top of this, and then transmit three
+	dummy bits at the begining as the decoder.  The three will
+	cycle through all three states help ensuring level detection
+
+	An optional paramter of lastlvl can be provided, which is
+	the previous signal level transmitted.'''
+
+	r = []
+	for i in bits:
+		v = int(i, 2)
+		lastlvl = (lastlvl + 1 + v) % 3
+		r.append('%d' % lastlvl)
+
+	return ''.join(r)
+
+encoded = jm3coder('000' + encoded)
+
+print('jm3coded:', repr(encoded))
+
+# make a "stretched" bit string
+stretched = ''.join(encoded[i:i + 50] + encoded[i:i + 50][-1] for i in range(0, len(encoded), 50))
+print('stretched:', repr(stretched))
+
+def jm3decoder(trits, lastlvl=0):
+	'''Decodes a string encoded w/ jm3coder.
+
+	lastlvl should/must be provided which is the last rx'd level
+	(it must be 0, 1 or 2).
+	'''
+
+	lookup = {
+		(0, 1): 0,
+		(0, 2): 1,
+		(1, 2): 0,
+		(1, 0): 1,
+		(2, 0): 0,
+		(2, 1): 1,
+	}
+	r = []
+	for i in trits:
+		lvl = int(i, 3)
+		if lvl == lastlvl:
+			continue
+
+		r.append('%d' % lookup[(lastlvl, lvl)])
+		lastlvl = lvl
+
+	return ''.join(r)
+
+decoder = EncDec8B10B()
+
+stretched = jm3decoder(stretched)
+
+print(repr(stretched))
+
+print(repr(decoder.decode(stretched)))
+print(repr(decoder.decode('')))
+
 print('done')