#!/usr/bin/env python3
"""Verify the Pi <-> re-bba-rb J4 wiring BEFORE attempting a real EXI transfer.

Requires the FPGA to be running an EXI_J4=1 bitstream, which mirrors EXI onto
the J4 header and enables SB_IO pull-ups on the three EXI *inputs*.

  J4.1 GND    <-> Pi pin 25  GND
  J4.2 DBG0   <-- Pi pin 23  BCM11  EXI CLK    (FPGA input)
  J4.3 DBG1   <-- Pi pin 19  BCM10  EXI MOSI   (FPGA input)
  J4.4 DBG2   --> Pi pin 21  BCM9   EXI MISO   (FPGA OUTPUT - never drive)
  J4.5 DBG3   <-- Pi pin 24  BCM8   EXI CS_N   (FPGA input)
  J4.6 DBG4   --> Pi pin 22  BCM25  EXI INT_N  (FPGA OUTPUT - never drive)

Run:  sudo python3 exi_wirecheck.py
"""
import sys, time
import RPi.GPIO as GPIO

CLK, MOSI, MISO, CS_N, INT_N = 11, 10, 9, 8, 25
HDR = {11: "hdr23", 10: "hdr19", 9: "hdr21", 8: "hdr24", 25: "hdr22"}
DRIVEN_BY_PI  = [(CLK, "CLK", "J4.2"), (MOSI, "MOSI", "J4.3"), (CS_N, "CS_N", "J4.5")]
DRIVEN_BY_FPGA= [(MISO, "MISO", "J4.4"), (INT_N, "INT_N", "J4.6")]

fails, warns = [], []

def rd(pin, pull):
    GPIO.setup(pin, GPIO.IN, pull_up_down=pull)
    time.sleep(0.002)
    return GPIO.input(pin)

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
for p, _, _ in DRIVEN_BY_PI + DRIVEN_BY_FPGA:
    GPIO.setup(p, GPIO.IN, pull_up_down=GPIO.PUD_OFF)

print("=" * 66)
print("T0  CONTROL: pins known to be unwired MUST follow the internal pull.")
print("    Without this, a broken pull mechanism would silently turn every")
print("    T1 verdict into a false \'CONNECTED\'.")
print("=" * 66)
for pin, hdr in ((26, "hdr37"), (20, "hdr38"), (16, "hdr36"), (21, "hdr40")):
    u, d = rd(pin, GPIO.PUD_UP), rd(pin, GPIO.PUD_DOWN)
    ok = (u, d) == (1, 0)
    print(f"  BCM{pin:<2} {hdr}: pull-up={u} pull-down={d}  "
          f"{'pull works' if ok else '** PULL NOT WORKING - T1/T2 INVALID **'}")
    if not ok:
        fails.append(f"control pin BCM{pin} did not follow the pull; results below are meaningless")
    GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_OFF)

print()
print("=" * 66)
print("T1  FPGA-driven pins: value must NOT follow the Pi's internal pull.")
print("    An active driver (~ohms) beats the Pi's ~50k pull; a dead wire")
print("    follows it.  This test is decisive.")
print("=" * 66)
for pin, name, j4 in DRIVEN_BY_FPGA:
    up, dn = rd(pin, GPIO.PUD_UP), rd(pin, GPIO.PUD_DOWN)
    if up == dn:
        print(f"  {name:<5} {j4} BCM{pin:<2} {HDR[pin]}: pull-up={up} pull-down={dn}"
              f"  -> CONNECTED, FPGA driving {up}")
    else:
        print(f"  {name:<5} {j4} BCM{pin:<2} {HDR[pin]}: pull-up={up} pull-down={dn}"
              f"  -> ** NOT CONNECTED ** (follows the Pi's pull)")
        fails.append(f"{name} ({j4} -> BCM{pin}/{HDR[pin]}) is open")
    GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_OFF)

print()
print("=" * 66)
print("T2  FPGA-input pins: these carry SB_IO PULLUP=1 in an EXI_J4 build, so")
print("    a correct connection reads HIGH regardless of the Pi's pull.")
print("    Follows-the-pull = open.  Hard low = shorted.  Decisive either way.")
print("=" * 66)
for pin, name, j4 in DRIVEN_BY_PI:
    u, d = rd(pin, GPIO.PUD_UP), rd(pin, GPIO.PUD_DOWN)
    if (u, d) == (1, 1):
        print(f"  {name:<5} {j4} BCM{pin:<2} {HDR[pin]}: up=1 down=1 -> held HIGH: FPGA pull-up seen, CONNECTED")
    elif (u, d) == (1, 0):
        print(f"  {name:<5} {j4} BCM{pin:<2} {HDR[pin]}: up=1 down=0 -> follows the Pi pull: ** OPEN **")
        fails.append(f"{name} ({j4} -> BCM{pin}/{HDR[pin]}) is open - no connection")
    else:
        print(f"  {name:<5} {j4} BCM{pin:<2} {HDR[pin]}: up={u} down={d} -> hard LOW: ** SHORTED TO GND **")
        fails.append(f"{name} ({j4} -> BCM{pin}/{HDR[pin]}) is shorted low - an FPGA input with "
                     f"PULLUP=1 cannot read a hard 0")
    GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_OFF)

print()
print("=" * 66)
print("T3  Bridge scan on the Pi-driven lines (catches solder bridges on J4).")
print("    Drive one HIGH, hold the others as inputs with pull-down: any")
print("    victim reading HIGH shares copper with the aggressor.")
print("=" * 66)
for pin, name, j4 in DRIVEN_BY_PI:
    victims = [(p, n) for p, n, _ in DRIVEN_BY_PI if p != pin]
    for vp, _ in victims:
        GPIO.setup(vp, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
    GPIO.setup(pin, GPIO.OUT)
    GPIO.output(pin, 1)
    time.sleep(0.003)
    bad = [n for vp, n in victims if GPIO.input(vp) == 1]
    GPIO.output(pin, 0)
    GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_OFF)
    if bad:
        print(f"  drive {name:<5} HIGH -> ** BRIDGED to {', '.join(bad)} **")
        fails.append(f"{name} is bridged to {', '.join(bad)}")
    else:
        print(f"  drive {name:<5} HIGH -> no bridge to {', '.join(n for _, n in victims)}")

print()
print("=" * 66)
print("T4  Liveness: assert CS_N, clock slowly, see if MISO ever moves.")
print("    Proves CLK + CS_N reach the FPGA and MISO comes back, without")
print("    depending on a correct transaction.")
print("=" * 66)
for p in (CLK, CS_N, MOSI):
    GPIO.setup(p, GPIO.OUT)
GPIO.output(CLK, 1)          # Mode 3: CLK idles HIGH
GPIO.output(MOSI, 0)
GPIO.output(CS_N, 1)
GPIO.setup(MISO, GPIO.IN, pull_up_down=GPIO.PUD_OFF)
time.sleep(0.01)
idle = GPIO.input(MISO)
GPIO.output(CS_N, 0)         # assert
time.sleep(0.005)
seen = {GPIO.input(MISO)}
for _ in range(32):
    GPIO.output(CLK, 0); time.sleep(0.001)
    seen.add(GPIO.input(MISO))
    GPIO.output(CLK, 1); time.sleep(0.001)
    seen.add(GPIO.input(MISO))
GPIO.output(CS_N, 1)
GPIO.output(CLK, 1)
print(f"  MISO idle (CS_N high) = {idle};  levels seen while clocking = {sorted(seen)}")
if len(seen) > 1:
    print("  -> MISO CHANGES while clocking: the FPGA is responding. Chain alive.")
else:
    print("  -> MISO never changed. Either the FPGA isn't seeing CLK/CS_N, or")
    print("     it has nothing to send yet. Not conclusive on its own; the")
    print("     device-ID read is the real test.")
    warns.append("MISO static while clocking")

GPIO.cleanup()
print()
print("=" * 66)
if fails:
    print("WIRING FAULTS:")
    for f in fails:
        print("  -", f)
if warns:
    print("ADVISORY:")
    for w in warns:
        print("  -", w)
if not fails:
    print("No hard wiring faults found." if not warns else
          "No hard wiring faults; see advisories above.")
    print("Next: sudo python3 ~/exi_devid_rpi.py   (expect 04 02 02 00)")
sys.exit(1 if fails else 0)