779 ORCA — Online Reconfigurable Circuit with Adaptation :: Quicker, easier and cheaper to make your own chip!

How it works

ORCA is a self-optimizing, self-healing evolvable logic engine. It contains:

A CGP-style reconfigurable fabric — a 4×4 grid of cells, each an arbitrary 2-input Boolean function (4-bit LUT) with two 4:1 input muxes. Column 0 reads the 4 primary inputs; column c reads only column c−1 (strictly feed-forward, so combinational loops are impossible by construction). Two outputs are selected from the last column. The entire circuit is defined by a 132-bit genome.
An on-chip (1+1) evolution strategy. Each generation, a xorshift32 PRNG picks one genome bit to flip. An eval engine scores the resulting circuit against a 16-row × 2-output target truth table (fitness = correct outputs, with measured circuit speed as a lexicographic tiebreaker). Better-or-equal mutants are kept; worse ones are reverted via a single-entry mutation log (XOR is its own inverse). Optional simulated annealing accepts some worse mutants with decaying probability.
A settle-time sensor — a dont_touch delay-line that shrinks the fabric's compute window until it fails, measuring how fast the evolved circuit really is on this specific die. Evolution keeps optimizing speed after correctness is solved, exploiting this die's process variation (Thompson's classic experiment, on modern silicon).

At reset the target is parity + AND-OR, so the chip evolves with no host attached: LEDs on uo_out[7:4] climb as fitness converges and uo_out[3] lights when solved. A bit-banged serial interface (24-bit command frames on ui_in[4:6], response on uio[3]) exposes every CSR: target truth table, genome read/write, PRNG seed, fault injection, annealing temperature, fitness counters, and the settle-tap measurement.

Demos: EVOLVE (converge on any loaded truth table), HEAL (inject stuck-at faults and watch evolution route around the dead cells), CHARACTERIZE (read per-die settle-tap profiles). HEAL needs no host: with ui[1] (anneal) held high, a press on ui[2] kills 3 cells, re-baselines fitness, and arms the annealing temperature — the solved LED drops, the fitness LEDs dip, and both recover as evolution re-routes around the dead cells.

How to test

Smoke test with no host: strap ui_in[0] (run) high, clock at 25 MHz, and watch uo_out[7:4] climb within a second; uo_out[3] = solved, uo_out[0] = generation heartbeat, uo_out[1] = evolving.

Host-free HEAL demo: additionally strap ui_in[1] (anneal) high; once solved, pulse ui_in[2] — solved drops and the fitness LEDs dip, then recover over a few seconds as evolution routes around the three dead cells.

With the demo board host tools (host/ in the repo):

tt_orca.py --port /dev/ttyACM0 id            # reads 0x08CA ("ORCA")
tt_orca.py ... seed 0xDEADBEEF               # reseed the PRNG
tt_orca.py ... run                           # start evolution
tt_orca.py ... poll                          # generation / fitness / accepts
live_plot.py --port /dev/ttyACM0             # live fitness plot
tt_orca.py ... inject-fault 0x4420 0x0000    # HEAL demo (kills 3 cells)

The full cocotb suite (test/) runs against the behavioral RTL with make -B and unit suites with make -B UNIT=fabric|fault|eval|es; the evolution end-to-end test is bit-exact against the Python golden model in model/.

External hardware

None required. Optional: scope on uio[4] (accept pulse trigger) and uio[5] (delay-line tap strobe) for the CHARACTERIZE demo; LEDs/PMOD on uo_out.

Pinout

Pin	Dir	Function
ui[0]	in	run (evolution enable)
ui[1]	in	anneal_en
ui[2]	in	fault_demo (rising edge kills 3 cells)
ui[3]	in	reserved
ui[4]	in	ser_data
ui[5]	in	ser_shift
ui[6]	in	ser_exec
ui[7]	in	reserved
uo[0]	out	heartbeat (generation counter bit)
uo[1]	out	evolving
uo[2]	out	accept pulse
uo[3]	out	solved
uo[7:4]	out	best_fitness[11:8]
uio[3]	out	ser_out (serial response)
uio[4]	out	scope trigger (= accept pulse)
uio[5]	out	settle-sensor tap strobe
uio[7]	out	fabric PO0 live

#	Input	Output	Bidirectional
0	run_ena	heartbeat	unused
1	anneal_en	evolving	unused
2	fault_demo	accept_pulse	unused
3	reserved	solved	ser_out
4	ser_data	best_fitness_8	scope_trigger
5	ser_shift	best_fitness_9	settle_probe
6	ser_exec	best_fitness_10	unused
7	reserved	best_fitness_11	po_0

779 ORCA — Online Reconfigurable Circuit with Adaptation