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Screen Reference

Navigation overview

The display has a single 64×128 px area (10 columns × 16 rows of text). When connected, content is organised into menus (horizontal) and screens (vertical within a menu).

← LEFT / RIGHT →    switches menu
↑ UP / DOWN ↓       switches screen within the current menu
SELECT              context action (varies per screen)

Menu order

Cockpit  ←→  Experimental  ←→  Debug  ←→  DTC  ←→  Settings

Experimental and Debug screens only appear in uno_debug builds compiled with -D OBD_EXPERIMENTAL_SCREENS.

Cockpit

Live sensor data. No SELECT action — data updates automatically every ~177 ms.

Instruments cluster (address 0x17)

One screen showing all values at once:

SPD:xxx  RPM:xxxx
CLT:xxx  OIL:xxx
OLV:x OPR:x AMB:xx
ODO:xxxxxxxxxx
FUL:xx  FSR:xxxxx
TIME:xxxxxxxxx
L/100:xxxxx L/h:xxxx
km:xxxxx  L:xxxxx
Field Meaning Unit
SPD Vehicle speed km/h
RPM Engine speed rev/min
CLT Coolant temperature °C
OIL Oil temperature °C
OLV Oil level OK 1=OK, 0=low
OPR Minimum oil pressure bar
AMB Ambient temperature °C
ODO Odometer km
FUL Fuel level L
FSR Fuel sender resistance Ω
TIME ECU uptime seconds
L/100 Fuel consumption rate since connection L/100 km
L/h Hourly fuel consumption L/h
km Trip distance since connection km
L Fuel burned since connection L

Engine ECU (address 0x01)

Two screens — UP/DOWN to switch:

Screen 0:              Screen 1:
RPM:xxxx  V:xxxxx      TBa:xxxxx STa:xxxxx
T1:xx T2:xx T3:xx      mbar:xxxx bits:xxxxxxxx
LAM:xxx LAM2:xxx
LOAD:xxx

Experimental

Raw measurement group values. Only visible in uno_debug builds.

Grp: XX

V1: XXXXXXX
U1: UUUUUU

V2: XXXXXXX
U2: UUUUUU

V3: XXXXXXX
U3: UUUUUU

V4: XXXXXXX
U4: UUUUUU
  • Grp — the measurement group number currently being read
  • V1–V4 — decoded value for each of the 4 measurement slots
  • U1–U4 — unit string for each slot (e.g. km/h, rpm, °C)

SELECT toggles between slot pairs: slots 0/1 ↔ slots 2/3.

Debug

Internal diagnostics. Only visible in uno_debug builds.

Con: 1        (software serial listening)
Ava: 0        (bytes available in RX buffer)
BC: 42        (KWP block counter)
KWP: Sensor   (current KWP mode)
Grp: 3        (measurement group being polled)
Adr: 0x17     (ECU address)
Baud:9600     (baud rate)
Att: 0        (connection attempt count)
Sim: N        (simulation mode active?)
RAM: 834      (estimated free RAM, bytes)

Use this screen to verify the connection parameters and monitor RAM during development.

DTC (Fault Codes)

Read and clear Diagnostic Trouble Codes stored in the ECU.

Main menu

DTC Menu

>Read
 Clear
 Show

DTCs: --

UP/DOWN moves the > cursor between the three actions. SELECT executes the highlighted action.

Action What it does
Read Sends a Read Faults request to the ECU and stores up to 16 DTCs
Clear Sends a Delete Faults request to the ECU
Show Opens the DTC list sub-view (only useful after a Read)

The DTCs: counter at the bottom shows -- until a Read is performed, then shows the count returned by the ECU.

Show sub-view (4 DTCs per page)

DTCs 1-4
#1  E:16825
    S:237
#2  E:17544
    S:64
#3  E:XXXXX
    S:XXX
#4  E:XXXXX
    S:XXX

U/D:pg  Sel:bk
  • E: — raw error code (decimal)
  • S: — status byte (decimal)
  • UP/DOWN pages through groups of 4; SELECT returns to the main menu

Decoding DTC codes

DTC codes from VAG KWP-1281 ECUs are VAG-specific 5-digit codes, not standard OBD-II P/U/B/C codes. To look up what a code means:

  • VCDS label files — Ross-Tech VCDS label file archive maps codes to plain-text descriptions for each ECU part number.
  • Ross-Tech Wiki — wiki.ross-tech.com has fault code lists and troubleshooting guides organized by code.
  • OBD-Codes.com — searching VAG XXXXX (e.g. VAG 16825) often returns a description and likely cause.
  • Your ECU's label file (e.g. 1J0-920-xx0.LBL for the instruments cluster) lists what each fault code means for that specific module.

The status byte indicates how the fault was recorded:

Bit Meaning
0 Fault is currently present
4 Fault is intermittent (sporadic)
5 Fault was present, now gone

Settings

Settings

>Exit
 KWP: Sens

UP/DOWN moves the cursor. SELECT acts on the highlighted item.

Item SELECT action
Exit Ends the ECU session cleanly and returns to the startup setup menu
KWP: Cycles the KWP mode: ACK → Grp → Sens → ACK …

KWP modes

Display Mode Behaviour
ACK Acknowledge only Sends keepalive blocks only — no sensor data is read. Useful to hold a session open without loading the ECU.
Grp Read Group Reads measurement groups sequentially (groups 1, 2, 3, …). This is the normal operating mode.
Sens Read Sensors Reads individual sensor channels. Slower than group mode but more granular.

Changing the mode takes effect on the next KWP cycle without disconnecting.

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