GpioShutdownService now also for C4

[joerg]

Link: viewtopic.php?f=137&t=21386

Tested on Voodiks LineageOS16.

[rooted]

You are putting the C4 in your car system?

[joerg]

Not ready with my thoughts. The C4 is for its power supply not compatible with the interface board I made once for the C2. As I looked into the schematic, it can't be supplied by the 5V pins at the 40pin header.

[joerg]

I have tested now an ON/OFF circuit with an ATiny85. It disconnects the C4 from 12V car voltage by a P-Ch Mosfet 10s after a watchdog signal has stopped. When ignition becomes on again, the voltage is switched on for 45 seconds, then watchdog signal must be there to overtake. The watchdog signal is generated by the app. When the C4 is switched off, the Atiny85 goes to sleep and the current goes down to 70uA.
I'm not yet ready with my thoughts. I need to test also a RTC and a PWM for a fan. Why to use a fan? I saw in the specs that it goes to 75°C to throttle. But this is made at 25°C ambient temperature. What is if in summer time the car heats up to > 50°C?

[joerg]

This is a very first design of an interface board, far away from ready.

Bildschirmfoto vom 2020-05-02 19-32-03.png (29.91 KiB) Viewed 967 times

I would add also
- a reset button that goes to Header.36 and to PB1 to bridge the watchdog for 40 seconds.
- a DS3231 RTC
- a pwm fan transistor

In the power part entry there is a voltage limiter circuit with TVS diode and coil. This would limit voltages above 15 V. The fuse should protect against short circuit, if the diode become faulty due to overload.

[joerg]

As I wrote, I'm not yet ready with my thoughts. I have measured now the current consumption in power off mode, connected the VU7+ and a 4G usb modem. The C4 takes 17mA. The power mosfet in this circuit may not be necessary! With this current it takes around a half year to drain the cars battery. Recommendations are highly appreciated. I am not a car expert. What would happen if I let my car some weeks in winter time. Does it goes on if battery is weak?

[rooted]

It wouldn't hurt the battery, the idle drain of a modern cars electrical system is quite a bit more than 17mA already.

It's not healthy for a car battery to not be used for months without a battery tender hooked up anyway.

[joerg]

I think I made some progress. I would stay with the solution of switch off the power with a mosfet. But I found another way to check if the C4 is powered off. The former solution with a toggle bit lacks some seconds until the C4 is really powered down. Now I connect the 5V pin to the ATtiny. It changes to ~1.5V once it is shut down. The LED acts as indication and as a zener and so ensures that the voltage level is fine for the GPIO of the ATtiny.
Furthermore with the mosfet the C4 can be power cycled. For this I added the switch, a short press reboots the C4 (by the GpioShutdownService App), a long press of > 2s power cycles the C4. I looked to the voltage supplying the C4 to see if there are spikes when I do so, but no, no spikes. This is also only the last option, if driving the car and the C4 does not respond any more.
There is also a connection for a fan. To have the right time immediately after boot, there is also a DS3231 high precise RTC.
I will now strip a board, it takes some time...

C4 Car Interface.png (234.61 KiB) Viewed 532 times

[joerg]

A step forward. But I will sleep a night about it, before I order from PCB manufacture.
And not so nice that some 3d models are missing. I don't have the skills, better not the patience, to draw the missing ones and add them to KiCad.

C4 Car Interface Top.png (82.91 KiB) Viewed 703 times

C4 Car Interface Bot.png (59.11 KiB) Viewed 532 times

[rooted]

I love following your progress and the custom hardware you come up with.

[odroid]

Please consider adding an optical Toslink SPDIF output jack before ordering the nice PCB. I hope I am not too late.
I want to enjoy HiFi sound in my car. Sorry for bothering you.

[joerg]

Please consider adding an optical Toslink SPDIF output jack before ordering the nice PCB. I hope I am not too late.
I want to enjoy HiFi sound in my car. Sorry for bothering you.

You don‘t bothering me, never
Already done, the U4 is a PLT133.

[odroid]

Ah... nice!
I couldn't find the U4 in your schematics though.

[joerg]

Yes, I will update it later on.

[joerg]

Updated the missing 3d models and also the sheet. See above.
I learned how to make the 3d models with FreeCad and integrate them to KiCad. Too much work to draw the models with more details.
BTW. I will wait some parts to check, if I have planned the board correct.

[joerg]

GpioShutdownService works also on Android 10 / LineageOS17.1.