change km in speedo on serial cable

[jnsx7]

The speedometer can be reprogrammed by disassemble it and desolder the EEPROM chip from the board and write your own hex data in it.

I was wondering is it possible to write the mileage on a speedometer with a usb to serial cabel and without even disassemble it, using only its pins.

I tried it with an USB-RS232 cable and a simple python code and got this output.
file.txt (http://www.digital-kaos.co.uk/forums/attachment.php?attachmentid=571356&stc=1&d=1542023233)

Can anybody help me figure this out or show the way where i should go?

Thank you!

[BraLaas]

Use eeprom clip and bridge crystal

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[jnsx7]

yes i know. i can do the writing. i am just curious and challenged myself do it somehow with the serial data pin.

[BraLaas]

Not tried, afraid of losing money haha
Eeproming works for me

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[mikkhh]

what speedo are we talking about? what pins you connected to ? send your python script...

[jnsx7]

#!/usr/bin/env python# -*- coding: utf-8 -*-
import serial


rs232 = serial.Serial(
port = '/dev/tty.usbserial',
baudrate = 9600,
parity = serial.PARITY_NONE,
stopbits = serial.STOPBITS_ONE,
bytesize = serial.EIGHTBITS,
timeout = 1
)


f=open("file.txt","w")
i = 0
while True:
i+=1
string = ""
c = rs232.read()
for i in range(16):
string += c
string+='\n'
f.write(string.encode('hex'))
print string.encode('hex')


f.close()




The speedo's serial number is 67261-08. It has a 93c66 eeprom. I plugged in the power source, and the second pin is the serial data based on this wiring diagram.571387
I connected the serial data pin to my usb-rs232 cable to the rx pin.
571388