Write a Gumnut subroutine that performs the function of the circuit described in Exercise 8.8. The subroutine takes an 8-bit unsigned binary amplitude value in r2 and outputs a corresponding value to an 8-bit register at port address 28, connected to the cathodes of an 8-LED commonanode bar display.

Exercise 8.8

Some digital audio applications use an LED bar display, consisting of a row of LED indicators to display the volume level of the audio signal. Assuming that the loudness is proportional to the logarithm of the signal amplitude, we can work out which LEDs to light by finding the left-most 1 bit in the unsigned binary number representing the amplitude. Design a circuit to drive an 8-LED common-anode bar display, given an 8-bit unsigned binary amplitude value.