The last log (Bit shuffling: what goes where ?) explains how the address bits are shuffled. Once the logical value and all the modes/options are obtained, these informations are compiled to generate a 32-bits word that is output to the file, which will program the Flash.

There are two conversion functions : hexadecimal and decimal. They are very similar and in fact can be merged into one, since the base parameter can work very well with this system *(I just realise that in ASCII systems, it's better to have separate conversion routines, but here it's pointless)*. So let's just forget about function pointers...

Given the **base** parameter, it's easy to decompose the number into digits. There is only one corner case to deal with : what to display when the input is zero. Of course it should display ___0 (and not a void screen, or else people wonder if the circuit works at all) but there are 2 ways to achieve this :

- initialise the display to ___0 and use a while(>0){} loop (which is not entered in the only case where it
**is**zeo) - or initialise to nothing (____) and use a do..while (repeat...until) so the remainder of zero is written at least once.

The 2nd choice is better because the init value is all-cleared and the corner case happens only once, the do-while loop is lighter.

So we have the following code:

```
DigitLUT=[ "0", "1", "2", "3", "4", "5", "6",
"7", "8", "9", "A", "B", "C", "D", "E", "F"];
// The previously described recursive function
function recurse( index, logic, sign, zero_ext, base) {
msg+=" "+logic;
if (index>0){ //0) {
var bit=BinLUT[index--];
recurse(index, logic, sign, zero_ext, base);
if (bit < 0) {
// special code for the modes
switch(bit) {
case -1: sign=1; break;
case -2: zero_ext=42; break;
case -3: base=16; break;
}
}
else
logic|= 1 << bit;
recurse(index, logic, sign, zero_ext, base);
}
else {
// This is a "leaf" call,
// where conversion takes place:
var i=0; // index of the digit;
var d; // the digit
var m="\n";
do {
d=(logic % base)|0;
logic= (logic/base)|0;
m=DigitLUT[d]+m;
} while (logic > 0);
msg+=" - "+m;
}
}
```

This code seems to work pretty well (once you solve rounding/FP issues with JavaScript by ORing 0)

```
------ -1
0 0 0 - 0
16384 - 16384
32768 32768 - 32768
49152 - 49152
------ -3
0 0 0 0 0 - 0
16384 - 4000
32768 32768 - 8000
49152 - C000
```

This code is directly inspired by traditional conversion functions from binary to ASCII. However our case differs substantially from an ASCII terminal because each new iteration writes to a different digit, corresponding to different codes.

In JavaScript or other similar languages, this is where multi-dimensional arrays become useful: there are 5 arrays (one for each digit) with 16 sub-arrays (for all the values). The counter **i** starts to be useful...

Well, being a rebel, I prefer to use a single array with 5×16 entries and increment **i** by 16.

```
var i=0; // index of the digit;
var d; // the digit
var m="\n";
do {
d=(logic % base)|0;
logic= (logic/base)|0;
m=DigitLUT[d+i]+m;
i+=16;
} while (logic > 0);
```

Then, it's "only a matter" of generating the rght bit pattern for each number.

Yes, the time has come to work on this...

The data pins are connected to the respective segments:

D 1 2 0 F2 1 F1 2 F3 A3 3 G3 C3 4 C1 G1 5 B1 F0 6 D1 E1 7 C0 D0 8 A2 B2 9 A1 F1 10 E3 D3 11 F2 B3 12 E2 G2 13 G0 E0 14 D2 C2 15 B0 A0Conversely, and more interesting, the segments are connected to the following data pins (+16 means connected to phase F2)

```
DigitPins=[
// A B C D E F G
[ 15+16, 15 , 7 , 7+16, 13+16, 5+16, 13 ],
[ 9 , 5 , 4 , 6 , 6+16, 9+16, 4+16 ],
[ 8 , 8+16, 14+16, 14 , 12 , 11 , 12+16 ],
[ 2+16, 11+16, 3+16, 10+16, 10 , 2 , 3],
];
```

Let's combine these pin numbers with the list of active segments (0=A, 1=B, etc.)

```
Numbers=[
[ 0, 1, 2, 3, 4, 5 ], // 0
[ 1, 2 ], // 1
[ 0, 1, 3, 4, 6 ], // 2
[ 0, 1, 2, 3, 6 ], // 3
[ 1, 2, 5, 6 ], // 4
[ 0, 2, 3, 5, 6 ], // 5
[ 0, 2, 3, 4, 5, 6 ], // 6
[ 0, 1, 2 ], // 7
[ 0, 1, 2, 3, 4, 5, 6 ], // 8
[ 0, 1, 2, 3, 5, 6 ], // 9
[ 0, 1, 2, 4, 5, 6 ], // A
[ 2, 3, 4, 5, 6 ], // B
[ 0, 3, 4, 5 ], // C
[ 1, 2, 3, 4, 6 ], // D
[ 0, 3, 4, 5, 6 ], // E
[ 0, 4, 5, 6 ] // F
];
```

(ok this looks a lot like what I have done already for the #Discrete YASEP at "Redneck" disintegrated 7 segments decoder)

The first four digits can be compiled with these two arrays. The fifth digit is explained in the very first log: Decoding the extra digit

Value: 0 1 Y 2 W + Z 3 Y + Z 4 X + Y 5 X + Z 6 W + X + Z Intermediate coding: W = F1, ph=1 (phase 2) X = F2, ph=1 (phase 2) Y = F1, ph=0 (phase 1) Z = F2, ph=0 (phase 1)

Knowing (from above) the values of F1, F2 and the phases, it's easy to make the values by hand.

```
Y = 1 << /*F1 =*/ 1;
Z = 1 << /*F2 =*/ 0;
W = 1 << /*F1+16 =*/ 17;
X = 1 << /*F2+16 =*/ 16;
SegmentLUT={
33: Y , // 1
34: W + Z, // 2
35: Y + Z, // 3
36: X + Y , // 4
37: X + Z, // 5
38: W + X + Z // 6
};
```

Now, a simple nested triple-loop combines the segments and the digits.

```
var k=0;
for (var j=0; j<4; j++) { // iterate the digits
for (var i=0; i<16; i++) { // iterate the values
var n=0;
// iterate the segments
for (var l=0; l< Numbers[i].length; l++)
n |= 1 << DigitPins[j][Numbers[i][l]];
// save the accumulated value
SegmentLUT[k++]=n;
}
}
```

You can check the result with the following code:```
function toBin(n) {
var m="", c;
for (var i=0; i<32; i++) {
c=" ";
if (n & 1)
c="#";
m=c+m;
n=n>>>1;
}
return m;
}
for (var i=0; i<=70; i++)
msg+=i+" "+toBin(SegmentLUT[i])+"\n";
```

This shoudl give you something like that:

From there, things become pretty easy :-)

For example, we have the values of all the numbers at every position so we can create the initial value of **0000**

```
var AllZero=
SegmentLUT[0]
|SegmentLUT[16]
|SegmentLUT[32]
|SegmentLUT[48];
```

Note that most segments (30 out of 35) are turned on so the power consumption is close to maximal. Maybe zero-extension is not such a good idea after all but we'll see in practice... Now we can return to the leaf call of the recursive function. Here is what must be done:

- unconditionally remove the precedent digit ("clear" with a ~8) from the
**zero_ext** - lookup the new pattern from
**SegmentLUT**and add it to**zero_ext** - output the result

```
var n=zero_ext;
do {
d=(logic % base)|0;
logic= (logic/base)|0;
n = (n & ~SegmentLUT[i+8])
| SegmentLUT[i+d];
i+=16;
} while (logic > 0);
output(n);
```

I have suffered a few lame inattention bugs (thanks to JS' weak checking) but the whole program works like a charm and must now be ported to C.

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