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'''Connecting the serial port is very easy, it's only 3 wires, GROUND is one of them''' '''GROUND is really important, often neglected, and in some cases, confusingly "connection kinda works apparently", but unreliable''' (eg VemsTune connects, but error during firmware upload). * either missing ground connection. ** eg. EC18/17 can be 2nd heater FET (NFET) output, or input; so '''use EC36/26 as signal ground''', do NOT assume that EC18/pin17 is GND (especially when swapping ECUs; maybe it was GND in old ECU, and not on the new; DVM diode mode measurement is quick and useful: 0mV indicates wired connection). * in trickier cases, ground loops can also cause noise (communication problems). Eg. some notebook chargers can cause interference. ---- '''On the ECU, DSUB9 female is used for RS232''' (since the PC is DSUB9/male). '''ECU DSUB9 male is LCD so do NOT try to connect RS232 to that''' with any kind of adapter => damage could result. RS232 is widely used, see [http://www.aggsoft.com/rs232-pinout-cable/pinout-and-signal.htm rs232 pinout]. Note that DSUB25 (which is almost never used) standard has TX-RX swapped compared to DSUB9. (DSUB=DB). ---- === How to make the RS232 cable for GenBoard/VerThree === Only 3 wires are needed for the cable. Shielded cable is highly recommended in a production environment. Shield must be connected at only one side (either PC or GenBoard), so ground must have a dedicated wire (DSUB9/pin5) inside the (min. 3 wires + shield) cable. The cable should preferrably not run alongside ignition (or other noisy) wires. ||'''DB9 female'''||Direction ||'''SV2'''||'''EC18'''||'''Earphone plug'''|| || || '''3''' ||--> ||1 ||EC18-pin14 ||RING ||Data transmitted by PC, '''received by genboard''' || || '''2''' ||<-- ||2 ||EC18-pin15 ||TOP ||Data received by PC, '''transmitted by genboard''' || || '''5''' ||<-> ||3 ||use GND ||Base || Ground || || 9 || <-- || - || - || - || '''Optional +5V''', supply voltage (60mA) for RS232-bluetooth adapter. Check your adapter specs || SV2 is the 3 pin connector next to the MAX232 chip, near the regulator and EC18. Pin 1 on SV2 is the "top" pin, with GND on the side closest to the !EconoSeal loom connectors. Only the SV2 header is populated. The pinout of SV1 is the same. Pin 3 of SV1 is the pin closest to Pin 1 of SV2. The EC18-pin 14 and 15 are otherwise free pins that are often used (eg. fully assembled units shipped recently) for RS322. DB9 works well but using a 1/4" earphone plug looks cleaner in an automotive enviroment. Even if 3.5mm plugs is used in the Autronic harness their manual recommends using 1/4" plugs if it's installed in a panel. This is a good advice, go with the 1/4" plug. The biggest problem with 3.5mm is that most of the female connectors are low quality and will cause problems with time. [http://www.lammertbies.nl/comm/cable/RS-232.html RS232 Cable layouts] DB9 (==DSUB9) connector for PC/Genboard Communication: Please share the sources for above image. It counterrecmomends EC36-26 as GND for some unknown reason (EC36-pin26 is fine for this purpose). ---- '''How to use FBUS connection''' - TODO: detail useful with a device (or adapter cable) that doesn't have -+8V compatible RS232, just 0/3V serial connection (like PDA-s, mobile phones and their accessory-cables). Also good for bypassing the MAX232 for testing (eg. if MAX232 was killed by swapped RX-TX). For the PC=>AVR direction the trick is to '''tap onto the AVR-side of R52'''(=2k7, between the mcp3208 chip and LCD connector) to prevent conflict with the output of MAX232 (without unsoldering the MAX232). The '''AVR => PC direction is easy''', there should be no conflict with the MAX232's input (several inputs can listen on the same bus while only one can drive at a time). See UsbToFbus. ---- '''See also''' * GenBoard/Manual
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