Author: wmb Date: Fri Mar 8 03:22:11 2013 New Revision: 3598 URL: http://tracker.coreboot.org/trac/openfirmware/changeset/3598
Log: Neonode touchscreen - added nonlinearity test.
Modified: cpu/arm/olpc/nn-touchscreen.fth
Modified: cpu/arm/olpc/nn-touchscreen.fth ============================================================================== --- cpu/arm/olpc/nn-touchscreen.fth Thu Mar 7 10:10:51 2013 (r3597) +++ cpu/arm/olpc/nn-touchscreen.fth Fri Mar 8 03:22:11 2013 (r3598) @@ -916,11 +916,188 @@ ['] (.tsmsg) to .tsmsg ;
+\ Nonlinearity test + +d# 2000 constant #pts-max + +#pts-max /w* value /buf +0 value xbuf +0 value ybuf +0 value #pts + +: alloc-bufs ( -- ) + /buf alloc-mem to xbuf + /buf alloc-mem to ybuf + 0 to #pts +; + +: free-bufs ( -- ) + xbuf /buf free-mem + ybuf /buf free-mem + 0 to #pts +; + +: +w@ ( adr index -- w ) wa+ w@ ; +: +w! ( w adr index -- ) wa+ w! ; + +: add-pt ( w.x w.y -- ) + #pts #pts-max u< if + ybuf #pts +w! + xbuf #pts +w! + #pts 1+ to #pts + else + 2drop + then +; + +: list-pts ( -- ) + #pts 0 ?do + i . ." : " xbuf i +w@ . ybuf i +w@ . cr + loop +; + +: sum-over ( buf size -- sum ) + 0 -rot /w* bounds ?do ( sum ) + i w@ + ( sum' ) + /w +loop ( sum ) +; + +\ Maximum values, assuming max-x = 1200, max-y = 900, #pts = 2000 +\ max-x2 = 1200 * 1200 = 1,440,000 +\ max-xy = 1200 * 900 = 1,080,000 +\ max-Sx = 1200 * 2000 = 2,400,000 +\ max-Sy = 900 * 2000 = 1,800,000 +\ max-Sx2 = max-x2 * 2000 = 2,880,000,000 +\ max-Sxy = max-xy * 2000 = 2,160,000,000 + +\ The max value for the denominator Sx2 - (Sx)2/n occurs when +\ half the samples are 0 and the other half are max-x +\ max-denom = max-Sx2 / 4 = 720,000,000 + +\ A similar argument applies to the numerator, except that it +\ can be either negative or positive. But its maximum absolute +\ value is of the same order of magnitude as max-denom + +\ calculate the sum over x^2 (a double int) +\ The maximum value is max-x * max-x * #pts +\ For max-x = 1200 and #pts = 2000, max-Sx2 is 2,880,000,000 +: sum-x2 ( -- Sx2 ) + 0 #pts 0 ?do ( Sx2 ) + xbuf i +w@ ( Sx2 x ) + dup u* + ( Sx2' ) + loop ( Sx2 ) +; + +\ calculate the sum over xy (a double int) +: sum-xy ( -- Sxy ) + 0 #pts 0 ?do ( S ) + xbuf i +w@ ( S x ) + ybuf i +w@ ( S x y ) + u* + ( S' ) + loop ( S ) +; + +0 value sum-x +0 value sum-y +: linear-least-squares ( -- intercept num den ) + xbuf #pts sum-over to sum-x + ybuf #pts sum-over to sum-y + + \ Slope numerator: SUM(xy) - (SUM(x)*SUM(y) / #pts) + + \ Sx max is #pts * xmax + \ Sy max is #pts * ymax + \ (Sx * Sy)/#pts max is xmax * ymax * #pts + sum-x sum-y #pts */ ( Sx*Sy/#pts ) + sum-xy swap - ( num ) + + \ Slope denominator: SUM(x^2) - (SUM(x)^2 / #pts) + sum-x sum-x #pts */ ( num Sx*Sx/#pts ) + sum-x2 swap - ( num den ) + \ Avoid division by 0 + dup 0= if 1+ then ( num den ) + + \ Calculate the intercept + 2dup sum-x #pts / -rot */ ( num den slope*Sx ) + + sum-y #pts / ( num den slope*Sx mean-y ) + swap - -rot ( intercept num den ) +; + +: do-point ( x y -- ) 2dup add-pt dot ; + +\ draw line across screen from left to right +: line-in-x ( intercept num den -- ) + screen-w 0 do ( intercept num den ) + 3dup i -rot */ + ( intercept num den point-y ) + dup 1 screen-h within if ( intercept num den point-y ) + i swap dot ( intercept num den ) + else ( intercept num den point-y ) + drop ( intercept num den ) + then ( intercept num den ) + loop ( intercept num den ) + 3drop ( ) +; +\ draw line from top to bottom of screen +: line-in-y ( intercept num den -- ) + swap rot ( den num intercept ) + screen-h 0 do ( den num intercept ) + 3dup i swap - ( den num intercept den num y-b ) + -rot */ ( den num intercept point-x ) + dup 1 screen-w within if ( den num intercept point-y ) + i dot ( den num intercept ) + else ( den num intercept point-y ) + drop ( den num intercept ) + then ( den num intercept ) + loop ( den num intercept ) + 3drop ( ) +; +: draw-line ( intercept num den color -- ) + pixcolor ! ( intercept num den ) + 2 pick abs 2 pick abs > if line-in-y else line-in-x then +; + +0 value err2 +: nonlinearity ( intercept num den -- mean-sq-nonlinearity ) + 0 to err2 ( intercept num den ) + #pts 0 ?do ( intercept num den ) + 3dup ( intercept num den intercept num den ) + xbuf i +w@ ( intercept num den intercept num den x ) + -rot */ + ( intercept num den predicted-y ) + ybuf i +w@ - ( intercept num den error ) + dup * ( intercept num den error^2 ) + err2 + to err2 ( intercept num den ) + loop ( intercept num den ) + 3drop ( ) + err2 #pts / ( Serror2/#pts ) +; + +\ TODO: +\ 1) Message and retry if slope and intercept not approximately correct +\ slope can be checked with +\ ( num den ) h# 10000 -rot */ LOW HIGH within +\ ( expected slope is negative , so LOW and HIGH are negative ) +\ 2) Establish threshold for nonlinearity and fail if exceeded +\ 3) Perhaps integrate the nonlinearity test with the targets test?
: scribble - ev( ['] dot ev )ev + alloc-bufs + ev( + 0 d# 27 at-xy ." Follow the line. Type a key to exit" cr + screen-h 6 - screen-h negate screen-w blue draw-line + ['] do-point ev + linear-least-squares ( intercept num den ) + 3dup red draw-line ( intercept num den ) + ." Nonlinearity: " nonlinearity .d cr + d# 5000 ms + )ev + free-bufs ;
+\ : scribble +\ ev( ['] dot ev )ev +\ ; +
0 value dx 0 value dy
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