LCD panel serial protocol correct but not working on Ultra 6 Plus — troubleshooting help?

▎ Solved it. Turns out the plain E / L string protocol from this thread (and the Nexenta forum post) is directionally right but missing two details that made it silently fail no matter what baud rate or framing I tried:

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▎ 1. The panel's PIC firmware needs the port left at its default termios settings — don't stty it to anything explicitly, just open and write.

▎ 2. Every line write needs a cursor-position command immediately before it — C <col_hex> <row_hex>\r — even if you already positioned it earlier. Skipping this is why bare L text\r never did anything.

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▎ I found this by pulling NETGEAR's own GPL source for RAIDiator-x86 (readynas-x86-kernel-modules/pro/lcd/nv6lcd.c in the 4.2.27 GPL release — their live download portal blocks bots, but it's recoverable via the Wayback Machine's CDX API if anyone else needs to dig up old NETGEAR GPL releases).

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▎ Full command set from that driver:

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▎ | Command | Meaning |

▎ |---------------------------|---------------------------------------|

▎ | E\r | Clear screen |

▎ | D 0|1|2\r | Backlight off / on / dim |

▎ | P 0\r | Stop progress bar (sent at init) |

▎ | F 0\r | Font select |

▎ | C <col_hex> <row_hex>\r | Position cursor (hex, no 0x) |

▎ | L<26-char padded text>\r | Write text at current cursor position |

▎ | B 8 A 0 <8 hex bytes> 0\r | Draw an 8x10 disk-status bitmap icon |

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▎ Disk icons sit at columns 0/8/10 (hex), row 0 for disks 1-3 and row D for disks 4-6. Text lines start at column 18 (right after the icon columns).

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▎ Working Python driver, port /dev/ttyS1, one open/write/close cycle per command:

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▎ #!/usr/bin/env python3

▎ import os, sys, time

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▎ PORT = "/dev/ttyS1"

▎ DISK_POS = {1: "0 0", 2: "8 0", 3: "10 0", 4: "0 D", 5: "8 D", 6: "10 D"}

▎ BITMAP_STD = {

▎ 1: "B 8 A 0 7F 41 49 59 49 49 5D 41 7F 0",

▎ 2: "B 8 A 0 7F 41 5D 45 5D 51 5D 41 7F 0",

▎ 3: "B 8 A 0 7F 41 5D 45 5D 45 5D 41 7F 0",

▎ 4: "B 8 A 0 7F 41 55 55 5D 45 45 41 7F 0",

▎ 5: "B 8 A 0 7F 41 5D 51 5D 45 5D 41 7F 0",

▎ 6: "B 8 A 0 7F 41 5D 51 5D 55 5D 41 7F 0",

▎ }

▎ BITMAP_BLANK = "B 8 A 0 7F 41 41 41 41 41 41 41 7F 0"

▎ BITMAP_FAIL = "B 8 A 0 7F 41 63 55 49 55 63 41 7F 0"

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▎ def _send(cmd):

▎ fd = os.open(PORT, os.O_RDWR)

▎ os.write(fd, cmd.encode())

▎ os.close(fd)

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▎ def _delay(ms):

▎ time.sleep(ms / 1000.0)

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▎ def clear():

▎ _delay(100); _send("E\r")

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▎ def backlight(mode):

▎ _send("D %d\r" % {"off": 0, "on": 1, "dim": 2}[mode])

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▎ def disk_icon(num, state):

▎ bitmap = {"std": BITMAP_STD[num], "blank": BITMAP_BLANK, "fail": BITMAP_FAIL}[state]

▎ _delay(150)

▎ _send("C %s\r" % DISK_POS[num])

▎ _send(bitmap + "\r")

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▎ def _line(row_hex, text):

▎ _delay(100)

▎ _send("C 18 %s\r" % row_hex)

▎ _send("L" + text[:26].ljust(26) + "\r")

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▎ def line1(text): _line("0", text)

▎ def line2(text): _line("D", text)

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▎ def init_screen():

▎ _delay(100); _send("P 0\r")

▎ _delay(100); _send("P 0\r")

▎ clear()

▎ _delay(100); _send("E\r")

▎ _delay(100); _send("D 1\r")

▎ _delay(100); _send("D 1\r")

▎ for d in range(1, 7):

▎ disk_icon(d, "blank")

▎ _delay(100); _send("F 0\r")

▎ line1("ReadyNAS")

▎ line2("")

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▎ if __name__ == "__main__":

▎ action = sys.argv[1]

▎ if action == "init": init_screen()

▎ elif action == "clear": clear()

▎ elif action == "line1": line1(sys.argv[2])

▎ elif action == "line2": line2(sys.argv[2])

▎ elif action == "backlight": backlight(sys.argv[2])

▎ elif action == "disk": disk_icon(int(sys.argv[2]), sys.argv[3])

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▎ Run as root, e.g. sudo python3 nv6lcd.py init or sudo python3 nv6lcd.py line1 "hello".