u/Dismal-Divide3337

For over 40 years I have designed hardware, firmware and software by the same standards. I have treated the currently available Renesas RX processor in completely the same manner that I once did the first z80 processors that I bought. The z80 was so ingrained that I eventually moved to the 64180 as shown in the image. I wire-wrapped a z80 based microcomputer of my own in 1977. I used an old (even old then) PDP switch panel to hand toggle in code to run.

On the RX63N based product that we do still produce and actually ship to users, not only have I done the hardware, I have not used any 3rd party code. Not even the Standard C Library that the Renesas e2studio IDE wants to force on me. I have authored every byte in my OS. I have even had to reverse engineer what is accessible through JTAG so as to accommodate production program and test without 3rd party dependence.

That 100MHz RX board supports its own JVM, handles TLSv1.2 and SSH/SFTP. Its OS confuses most into thinking it is a Linux boot. It is not.

If your attraction to vintage computing is the fact that you can understand EVERYTHING that the computer does. I can prove that you can still do that with current technologies. I will admit that the manufacturers of this stuff (Renesas) don't get why you would ever want to do that. I am definitely an outlier in their eyes. But they know what I have done. Am doing.

I am your classic "old beard" and if you want to challenge me, go for it. Help me build up r/jnior. I am setting that up, not to push product, but to share what we've created and its story. Some of that might amaze.

BTW, I have schematics for that board pictured. Why is there a z80 on an ISA card for a PC you might wonder? I also have the source code. That was written entirely in z80 assembler. I have even placed my 64180/z80 Macro Assembler on Github. I wrote that and that was all I had - what I used back then (and before). The firmware for that board still fully compiles. I admit that I haven't tried to boot that. I don't have a PC with an ISA bus to stick it in.

So my LH headlamp doesn't come up - no surprise. It's a low-mileage garage kept 2002 Firehawk. Last year it did the same but after I investigated it, it started working. So this time I thought that I would get a little deeper understanding.

This is my reverse engineering and estimate of the operation of the headlamp PCB. Someone someplace might have the detail for what I think is a custom ASIC.

Voltages on the 5-pin connector are proper so my issue is not upstream. RH and LH are separately fused so that is worth checking.

With the PCB out of its housing and installed in the car. I carefully connected the 5-pin connector. You do not want to get that on wrong. But I could stick on the 4-pin motor connector offset by 2 pins and get the LH circuit to run the RH headlamp motor. Albeit because the connector goes ABBA (great band BTW) it would go up when it was supposed to go down. But the fact that both sections of the PCB runs the motor absolves the circuit from fault.

So it is the LH motor. It doesn't twitch or show any life. I am thinking there is an oxidized brush or some dead spot. I am going to try to advance the motor cog so it sits in a different place while at the stops. Maybe that will bring it back to life. Haven't gotten to that.

But I thought my schematic might be of interest. I would welcome corrections or another to compare.

Basically the relay swaps the motor leads and thereby the direction. By default it is set to run headlamps up. The two MOSFETs drive the two motors. The ASIC activates the relay coil to run the lights down but can't do that until the key is OFF. It watches for Back EMF to tell if a motor is running, stalled or disconnected.

I am sure that the logic varies between models destined for different locales.