How do I do to show the temperature value in two display BCD 7-seg? What's the combinatorial circuit that I need to build? I don't know how to pass from binary to BCD and also use only 5 bits to goes from 0 to 32.
I had a rummage around the various image searches and drew a blank. All the BCD to seven-segment display drivers are 4-bit input devices. You could use combinational logic (NANDs or NORs) but it would get ridiculous.
Since you have the first bit working and are happy with it and maybe want to use this as a learning exercise, a simple solution would be to use a micro with 16 or 18 GPIO pins. You could use eight to read the AD0804, seven more to drive the segments of the seven-segment displays and two more to drive the common cathodes or anodes.
For even more fun you could reduce the I/O count to nine or ten, depending on whether you want decimal point display too. (You don't in your case.) This comes at the cost of seven or eight resistors.
(Your requirement is for 5-bit to dual seven-segment display without decimal point so modify accordingly.)
simulate this circuit – Schematic created using CircuitLab
Figure 1. The micro is configured to read the AD804 outputs in between strobing the seven-segment displays.
With the addition of R1 to R8 you may be able to economise on GPIO pins on the micro - to keep the size down and learn some more.
disable(GPIO8); // Tristate the seven segment common driver pin.
disable(GPIO9); // As above.
input(portA); // Configure port A as inputs.
delay(1); // Stabilise.
t = readTemperature(); // Read the 8-bit value on port A.
msd = t \ 10; // Most significant digit. (Integer division.)
lsd = t % 10; // Least significant digit. (Modulo arithmatic.)
output(portA, sevenseg(msd)); // Configure port A as outputs and setup
the seven-segment display pattern.
output(GPIO8, 1); // Strobe the first digit.
delay(x); // Give it some time to excite the retina.
output(GPIO8, 0); // Turn off 10s display.
output(portA, sevenseg(lsd)); // Repeat for units display.
It does what you want with only one chip and some code.