Hi!
I am in the process of starting a new "hobby" project(on Primer2/eventually, later, convert on Primer1) of an engine monitoring/diagnostic system (for divers sensors+ OBDII engine computer interface), specific for Audi/VW with ISO 9141-2 / ISO 14230 KWP2000 (Keyword
Protocol 2000) interface (VAG-com compatible).
The project would require a ISO 9141-2 interface chip connected to the UART extension port of Primer2.
One particularity for Audi/VW is that they require/use both K and L lines (with L being a sort of wakeup line for engine computer)
Most ISO 9141 inteface chips use only K line (there are also LIN transceivers with ISO 9141 compatibility , but use only K line, like NXP TJA1020) http://www.nxp.com/acrobat/datasheets/TJA1020_5.pdf
I have seen the ST L9637 used successfully for the so called VAG KKL (K and L lines) interface with FTDI FT232R (USB to RS232) chips (at 5 Volts).
The main problem seems to be with voltage compatibilities between Primer 2 UART on extension connector and ST L9637 since the L9637 seems to work at voltages above 4.5V and is (only?) TTL compatible.
The specs sheet for STM32F103VE, state USARTs - LIN "capability"
Any more info available on this?
So far my options would be:
1) use L9637 with a 12V to 5V supply if UART on extension connector is 5v tolerant.
2) add a voltage level converter(3.3 to 5V) of it is not 5v tolerant.
3)find a compatible 3.3v ISO 9141 interface chip alternative to L9637.
so far I am in the process of evaluating alternatives like NXP TJA1020 / MAXIM MAX13020 LIN Transceivers (compatible 3.3v)
also MC33290 which is said to be CMOS MCU compatible but does no specify compatible 3.3v.
Any suggestions, opinions, info would be very much appreciated.
Thanks.
-------------------------------
info"
# ISO 9141-2. This protocol has a data rate of 10.4 kbaud, and is similar to RS-232. ISO 9141-2 is primarily used in Chrysler, European, and Asian vehicles.
* pin 7: K-line
* pin 15: L-line (optional)
* UART signaling (though not RS-232 voltage levels)
* K-line idles high
* High voltage is Vbatt
* Message length is restricted to 12 bytes, including CRC
# ISO 14230 KWP2000 (Keyword Protocol 2000)
* pin 7: K-line
* pin 15: L-line (optional)
* Physical layer identical to ISO 9141-2
* Data rate 1.2 to 10.4 kbaud
* Message may contain up to 255 bytes in the data field
