with i2c buffer set at 32, 

here is the current microseconds used to output 768 reads to terminal (it would be faster to spi lcd)

but most of the time taken is from the math of the To calc function

+145000 getting cal values

complex math in To is 500000 math 

so total time is 645000 +getting ram from i2c. 

850000 microseconds 32words buffer
770000 64 word buffer
790000 128 word buffer //we are above the range of benefit here. 

what i want to do is 

1) buffer serial data so it instantly shows on screen.

2) use extra ram for LCD display functions.

https://hackaday.io/project/167533-faster-speed-how-optimize-math-and-process-tasks/log/168596-speed-up-i2c-faster-than-it-can-be-normally-caching-data-you-use

i use the mlx90640 sensor to store its ram values until i need them. the ram values always are updating so they need to be requested at each frame no matter what. i can read one ram cell at a time or all of them, but here is why you would only need to read between 32-64 at a time (assuming it all is with one capture and you are getting data quickly, or the sensor is in step mode)

each word has an average of ~20,000 microseconds for my project.  (with overhead of my code)

in the mlx90640 sensors case, each read of i2c requires a minimum of 7bytes +(2bytes each ram)

reading more than one byte at a time is more efficient.

1 word is at 22% efficient

16 words  80% efficient or 3.6 times faster than 1 byte

 32 words is 90% efficient. 4.1 times faster than 1 byte

64 words is 94% efficient 4.3 times faster than 1 byte

128 words is 97% efficient 4.4 times faster than 1 byte

btw here is the efficiency based on how many words are i2c cached.

efficiency overhead.  data received at a time.   efficiency level 
7(bytes) overhead 0word(0bytes):::::::::0
7(bytes) overhead 1word(2bytes):::::::::0.2222222222222222
7(bytes) overhead 2word(4bytes):::::::::0.36363636363636365
7(bytes) overhead 3word(6bytes):::::::::0.46153846153846156
7(bytes) overhead 4word(8bytes):::::::::0.5333333333333333
7(bytes) overhead 5word(10bytes):::::::::0.5882352941176471
7(bytes) overhead 6word(12bytes):::::::::0.631578947368421
7(bytes) overhead 7word(14bytes):::::::::0.6666666666666666
7(bytes) overhead 8word(16bytes):::::::::0.6956521739130435
7(bytes) overhead 9word(18bytes):::::::::0.72
7(bytes) overhead 10word(20bytes):::::::::0.7407407407407407
7(bytes) overhead 11word(22bytes):::::::::0.7586206896551724
7(bytes) overhead 12word(24bytes):::::::::0.7741935483870968
7(bytes) overhead 13word(26bytes):::::::::0.7878787878787878
7(bytes) overhead 14word(28bytes):::::::::0.8
7(bytes) overhead 15word(30bytes):::::::::0.8108108108108109
7(bytes) overhead 16word(32bytes):::::::::0.8205128205128205
7(bytes) overhead 17word(34bytes):::::::::0.8292682926829268
7(bytes) overhead 18word(36bytes):::::::::0.8372093023255814
7(bytes) overhead 19word(38bytes):::::::::0.8444444444444444
7(bytes) overhead 20word(40bytes):::::::::0.851063829787234
7(bytes) overhead 21word(42bytes):::::::::0.8571428571428571
7(bytes) overhead 22word(44bytes):::::::::0.8627450980392157
7(bytes) overhead 23word(46bytes):::::::::0.8679245283018868
7(bytes) overhead 24word(48bytes):::::::::0.8727272727272727
7(bytes) overhead 25word(50bytes):::::::::0.8771929824561403
7(bytes) overhead 26word(52bytes):::::::::0.8813559322033898
7(bytes) overhead 27word(54bytes):::::::::0.8852459016393442
7(bytes) overhead 28word(56bytes):::::::::0.8888888888888888
7(bytes) overhead 29word(58bytes):::::::::0.8923076923076924
7(bytes) overhead 30word(60bytes):::::::::0.8955223880597015
7(bytes) overhead 31word(62bytes):::::::::0.8985507246376812
7(bytes) overhead 32word(64bytes):::::::::0.9014084507042254
7(bytes) overhead 33word(66bytes):::::::::0.9041095890410958
7(bytes) overhead 34word(68bytes):::::::::0.9066666666666666
7(bytes) overhead 35word(70bytes):::::::::0.9090909090909091
7(bytes) overhead 36word(72bytes):::::::::0.9113924050632911
7(bytes) overhead 37word(74bytes):::::::::0.9135802469135802
7(bytes) overhead 38word(76bytes):::::::::0.9156626506024096
7(bytes) overhead 39word(78bytes):::::::::0.9176470588235294
7(bytes) overhead 40word(80bytes):::::::::0.9195402298850575
7(bytes) overhead 41word(82bytes):::::::::0.9213483146067416
7(bytes) overhead 42word(84bytes):::::::::0.9230769230769231
7(bytes) overhead 43word(86bytes):::::::::0.9247311827956989
7(bytes) overhead 44word(88bytes):::::::::0.9263157894736842
7(bytes) overhead 45word(90bytes):::::::::0.9278350515463918
7(bytes) overhead 46word(92bytes):::::::::0.9292929292929293
7(bytes) overhead 47word(94bytes):::::::::0.9306930693069307
7(bytes) overhead 48word(96bytes):::::::::0.9320388349514563
7(bytes) overhead 49word(98bytes):::::::::0.9333333333333333
7(bytes) overhead 50word(100bytes):::::::::0.9345794392523364
7(bytes) overhead 51word(102bytes):::::::::0.9357798165137615
7(bytes) overhead 52word(104bytes):::::::::0.9369369369369369
7(bytes) overhead 53word(106bytes):::::::::0.9380530973451328
7(bytes) overhead 54word(108bytes):::::::::0.9391304347826087
7(bytes) overhead 55word(110bytes):::::::::0.9401709401709402
7(bytes) overhead 56word(112bytes):::::::::0.9411764705882353
7(bytes) overhead 57word(114bytes):::::::::0.9421487603305785
7(bytes) overhead 58word(116bytes):::::::::0.943089430894309
7(bytes) overhead 59word(118bytes):::::::::0.944
7(bytes) overhead 60word(120bytes):::::::::0.9448818897637795
7(bytes) overhead 61word(122bytes):::::::::0.9457364341085271
7(bytes) overhead 62word(124bytes):::::::::0.9465648854961832
7(bytes) overhead 63word(126bytes):::::::::0.9473684210526315
7(bytes) overhead 64word(128bytes):::::::::0.9481481481481482
7(bytes) overhead 65word(130bytes):::::::::0.948905109489051
7(bytes) overhead 66word(132bytes):::::::::0.9496402877697842
7(bytes) overhead 67word(134bytes):::::::::0.950354609929078
7(bytes) overhead 68word(136bytes):::::::::0.951048951048951
7(bytes) overhead 69word(138bytes):::::::::0.9517241379310345
7(bytes) overhead 70word(140bytes):::::::::0.9523809523809523
7(bytes) overhead 71word(142bytes):::::::::0.9530201342281879
7(bytes) overhead 72word(144bytes):::::::::0.9536423841059603
7(bytes) overhead 73word(146bytes):::::::::0.954248366013072
7(bytes) overhead 74word(148bytes):::::::::0.9548387096774194
7(bytes) overhead 75word(150bytes):::::::::0.9554140127388535
7(bytes) overhead 76word(152bytes):::::::::0.9559748427672956
7(bytes) overhead 77word(154bytes):::::::::0.9565217391304348
7(bytes) overhead 78word(156bytes):::::::::0.9570552147239264
7(bytes) overhead 79word(158bytes):::::::::0.9575757575757575
7(bytes) overhead 80word(160bytes):::::::::0.9580838323353293
7(bytes) overhead 81word(162bytes):::::::::0.9585798816568047
7(bytes) overhead 82word(164bytes):::::::::0.9590643274853801
7(bytes) overhead 83word(166bytes):::::::::0.9595375722543352
7(bytes) overhead 84word(168bytes):::::::::0.96
7(bytes) overhead 85word(170bytes):::::::::0.96045197740113
7(bytes) overhead 86word(172bytes):::::::::0.9608938547486033
7(bytes) overhead 87word(174bytes):::::::::0.9613259668508287
7(bytes) overhead 88word(176bytes):::::::::0.9617486338797814
7(bytes) overhead 89word(178bytes):::::::::0.9621621621621622
7(bytes) overhead 90word(180bytes):::::::::0.9625668449197861
7(bytes) overhead 91word(182bytes):::::::::0.9629629629629629
7(bytes) overhead 92word(184bytes):::::::::0.9633507853403142
7(bytes) overhead 93word(186bytes):::::::::0.9637305699481865
7(bytes) overhead 94word(188bytes):::::::::0.9641025641025641
7(bytes) overhead 95word(190bytes):::::::::0.9644670050761421
7(bytes) overhead 96word(192bytes):::::::::0.964824120603015
7(bytes) overhead 97word(194bytes):::::::::0.9651741293532339
7(bytes) overhead 98word(196bytes):::::::::0.9655172413793104
7(bytes) overhead 99word(198bytes):::::::::0.9658536585365853
7(bytes) overhead 100word(200bytes):::::::::0.966183574879227
7(bytes) overhead 101word(202bytes):::::::::0.9665071770334929
7(bytes) overhead 102word(204bytes):::::::::0.966824644549763
7(bytes) overhead 103word(206bytes):::::::::0.9671361502347418
7(bytes) overhead 104word(208bytes):::::::::0.9674418604651163
7(bytes) overhead 105word(210bytes):::::::::0.967741935483871
7(bytes) overhead 106word(212bytes):::::::::0.9680365296803652
7(bytes) overhead 107word(214bytes):::::::::0.9683257918552036
7(bytes) overhead 108word(216bytes):::::::::0.968609865470852
7(bytes) overhead 109word(218bytes):::::::::0.9688888888888889
7(bytes) overhead 110word(220bytes):::::::::0.9691629955947136
7(bytes) overhead 111word(222bytes):::::::::0.9694323144104804
7(bytes) overhead 112word(224bytes):::::::::0.9696969696969697
7(bytes) overhead 113word(226bytes):::::::::0.9699570815450643
7(bytes) overhead 114word(228bytes):::::::::0.9702127659574468
7(bytes) overhead 115word(230bytes):::::::::0.9704641350210971
7(bytes) overhead 116word(232bytes):::::::::0.9707112970711297
7(bytes) overhead 117word(234bytes):::::::::0.970954356846473
7(bytes) overhead 118word(236bytes):::::::::0.9711934156378601
7(bytes) overhead 119word(238bytes):::::::::0.9714285714285714
7(bytes) overhead 120word(240bytes):::::::::0.97165991902834
7(bytes) overhead 121word(242bytes):::::::::0.9718875502008032
7(bytes) overhead 122word(244bytes):::::::::0.9721115537848606
7(bytes) overhead 123word(246bytes):::::::::0.9723320158102767
7(bytes) overhead 124word(248bytes):::::::::0.9725490196078431
7(bytes) overhead 125word(250bytes):::::::::0.9727626459143969
7(bytes) overhead 126word(252bytes):::::::::0.972972972972973
7(bytes) overhead 127word(254bytes):::::::::0.9731800766283525
7(bytes) overhead 128word(256bytes):::::::::0.973384030418251