The Pedestrian Horn

Dutch forum member OlafH dissected the pedestrian horn a bit and posted this picture.


The horn is a bit hard to get to, one has to remove the front bumper to get to it. I tried to analyse it a bit. Here is a summary of the most important components. Prepare to be amazed.

SPC5602: A generic processor, though aimed at the car industry, made by NXP. It’s current id is MPC5602P. It has 64KB data flash, 20KB RAM, 256KB code flash, and a PMW generator. MPC5602P

TPA3111Q1: A 10 Watt D-class (PWM) mono audio amplifier by Texas instruments. No real surprises on this one. TPA3111D1-Q1

UJA1076A: CAN transceiver, a nifty little chip, made by NXP. It can also acts as a power supply and watchdog. UJA1076A

25P16vpa:  16Mbit (2MB) flash memory, made by ST Microelectronics. I bet the sound files are stored here.  Enough for 2 minutes mp3 encoded data or 12 seconds of raw sound files. 25P16vpa

1334A: Stereo DAC. Hell, this horn is CD quality, they didn’t even use the PMW output of the main processor!!!! Also NXP. 1334A

7342: Dual hexfet. Basically an on-off switch, by International Rectifier, now Infineon: 7342

The horn resells for about 180 Euros. It is hooked up to the Electro CANbus, power, and a few more wires. While I haven’t touched it myself yet, I bet the sound selector push-button is wired directly to it.

By the way. Another name for a Pedestrian Horn is Vehicle Sound for Pedestrians or VSP, though this is officially a Nissan name and developed system.

Edit: Matthew posted a link to an in depth description of ZOE’s VSP in the comments. I’ve copied the file here on the CanZE blog should the link go dead. Thank you Mathew.

Edit: Thanks you Rudi42 for the additional picture of the location, and of course the custom project.

10 Comments on “The Pedestrian Horn

  1. Someone has to work out a hack on this so we can all drive around with F1 sounds, Pod racers, Tie Fighter, Knight Rider, Mysterons, crazy frog, imperial March, or just “Electric car… don’t walk in front of me being shouted out”.

  2. Quick question if somebody faced this before (Google seem to not know even in French). I’ve disconnected the 12v battery (- obviously), then connected it in a few days. The car’s pedestrian horn let a small hum then shut off. Then the next day I repeated the operation (in order to open the boot πŸ˜€ ) the horn would not turn off while the cabin button LED flashed and pressing it didn’t seem to have any effect. Gonna try tomorrow if this condition sticks.

    Car is without traction battery at the moment, so it might be related somehow, but maybe it’s something commonly known, thus asking.

    • Stupid question: is the battery still full? What you describe is somewhat familiar to my 12 volt being flattened to 5V (oops!). it might have been slowly emptied without the traction battery?

    • Nope πŸ™‚ Somebody should send me a trashed VSP and maybe I can see what’s on the flash eeprom.

  3. I think, the best idea is not to change the original design, but to complement the velocity based audio information with an additional pedestrian horn audio generation board. The pedestrian horn may be activated only on very slow velocity (parking place etc.) where the original horn does not sound.
    Therefore, the additional board only needs the supply voltage and the audio amplifier. Perhaps additionally a signal from the reverse gear can trigger a “beep-beep sound” for the pedestrians.

    If you are interested in, I already programmed an Arduino Nano board with such a program, including 10 audio files. You can find all project files in the going electric forum,