The hardware¶

What the unit physically is. Everything else on this site is about its software; this page is the box underneath it.

The board in one paragraph¶

A single-DIN Magneti Marelli head unit built around an NXP/Freescale MPC5121e PowerPC SoC (the e300 core this project executes in emulation), with 512 MB DDR2 and 4 GB NAND flash, plus a 16 GB internal microSD holding cartography and the jukebox. Radio and audio are a separate DIRANA2 DSP front end; navigation is a SiRFstarIV GPS receiver; Bluetooth is an Infineon PBA31308 module. The display is a 7-inch 800×480 panel on LVDS, optionally mirrored to a second output. An Apple authentication chip (MFI337S2313) sits on the USB path so the unit can talk to iPods/iPhones.

Logic core and generic peripherals¶

(The smeg-rce wiki additionally names the display controller as a PowerVR MBX; the spec says only "embedded display controller". Treat the MBX name as the wiki's attribution, not the spec's.)

Board variants¶

The spec lists variants A1, B1, B2, D1, D2, H1, H2. What changes:

• the second USB socket exists only on B1, B2, D1, D2, H1, H2;
• the second LVDS output (a copy of the first) exists only on D1 and D2;
• DAB is available only on B2 and D2;
• external video 1 (the rear camera) is not fitted on A1.

The A9 / B78 / E3 / T9 / G7 codes elsewhere in this site are car models, not board variants — they drive which HARMONY skin and user guide a unit gets, not which board it is built on.

Navigation¶

• 12-channel GPS receiver based on a SiRFstarIV processor.
• Nominal cold start under 40 seconds.
• GPS antenna: active, fed 5 V phantom power through a FAKRA code C (blue) connector.

Audio and radio¶

• Radio with three tuners, phase diversity, built around the DIRANA2 DSP and "LeafDice" analog tuners; RDS and TMC decoding.
• Power amplifier: class AB, 4 channels, 16 W RMS at 1 % THD (13.5 V, 4 Ω).
• External HiFi amplifier support: analog (booster) ×4, or digital ×2 driven over CAN.
• External mono CD reader: stereo inputs, half-differential, on three lines.
• AUX: stereo inputs, half-differential, on three lines.
• Microphone: analog mono.

The three audio paths¶

The spec describes the DSP's routing as three named paths:

When the GSM/Bluetooth module does its own echo cancellation, paths 2 and 3 are shorted into a single "audio process 4". This is the hardware under the software described in The audio module: the "AUX input" the unit switches on is the half-differential analog input of path 1.

Video out¶

• One LVDS pair to a 7-inch 800×480 TFT at 60 Hz.
• A second LVDS pair (a copy of the first) on D1 / D2.
• DGT display compatibility over CAN High Speed (touch feedback, brightness commands).

USB¶

• One customer USB 2.0 port, guaranteed 1 A at 4.75 V; a second on the variants above.
• An internal hub is present even on single-port units, to interface USB peripherals to the main MCU.
• Over-current/ESD protection (Maxim MAX16944) feeds an OVERCURRENT signal the software turns into a popup.
• The Apple chip is what makes iPod/iPhone USB work: the unit drives it over I²C and checks a code exchanged with the peripheral against a value in the chip.

Bluetooth¶

• Infineon PBA31308 module, with an internal printed antenna (an external-antenna BOM option exists).
• HFP and A2DP profiles.

Thermal management¶

This is a plausible cause of "the volume would not go up" reports on a hot dash — it is a hardware safety limit, not a software setting.

Power¶

• Supplied on the 40-pin connector: A12 +VBAT, A16 CAR_GND.
• Operating range 10–18 V; up to 24 V for one minute (unusual supply); load-dump protection opens the main switch above 18 V; reverse-battery protection.
• Standby current under 1 mA worst case at 12 V; normal mode up to ~13 A.
• A 15 A fuse in the 40-pin connector protects the unit and the CD changer; the CD changer output is additionally protected by an on-board 6 A fuse.
• Below 9 V some peripherals (amplifier mute, diagnostics) are disabled, but vital functions work above 4.75 V.

Connectors¶

Rear face:

• 40-pin main connector — Molex 91905-1225.
• LVDS display connector — Rosenberger D4S10F-40MA5-A / -D.
• USB rear connector — Hirose GT17HM-4P-2DSA.
• FAKRA antenna connectors: AM/FM1 code B (cream), FM2 code G (grey), GPS code C (blue), Bluetooth code D; DAB (where fitted) is orange.

40-pin connector — the pins the software cares about¶

The spec gives the full pin table as figures, so only the pins named in its prose are listed here (read):

The AUX input is half-differential on three lines (right, left, reference), 0.7 Vrms nominal, ~10–20 kΩ, 3.6–4.4 V DC bias — which is why the unit measures it with a detector and a threshold rather than treating it as a simple line-in. How the software does that is in The AUX signal path.

Mechanics¶

• 1-DIN system box, 900 g maximum.
• Installation angle: −5° to +45° (front-to-back); slope −15° to +15°.
• FAN cooled, driven by a temperature sensor.

What this does not tell you¶

• Nothing here is a supported service procedure. Opening the unit, removing it from the car and reflashing the front-panel MCU are all outside anything Magneti Marelli would endorse.
• Board variant is not read by any tool here. If a behaviour depends on which board a car has, this page is where to start looking, but the project has not correlated the two.
• The spec is from 2013 and describes the SMEG+ Integrated (5.x) generation. The successor (6.x) is a different board.