mbt28
Posts: 29
Joined: Wed Feb 04, 2015 10:35 am

Raspberry Pi IBUS and Powering

Wed Feb 04, 2015 11:38 am

Hello,

Within the release of Raspberry Pi 2, I decided to buy one. I would like to make a project which will replace BMW`s cd-changer. Raspberry pi will simulate it on ibus. Well for receiving and injecting data I will use mcp2025. Mcp2025 sends current over 8th leg if there is an active network over ibus line, and will goes to sleep if there is no network.
So I am thinking of using 5V version of MCP2025 over usb. But the biggest issue is waking up raspberry pi from usb. I need to hear your ideas in this part.
First, I would like to make this circuit as simple as possible. I think I can program raspberry pi to shutdown if it doesn’t receive any ibus signal for defined duration, but then circuit has to cut usb power as well. Then it should wake up if linbus transceiver receives any ibus signal. Can I send wake up signal to raspberry pi on usb(OTG)? Can I use 8th pins voltage as a wake up signal? Can I communicate in this way over usb as seen in my schematic?

Or should I give up with this idea and work on an additional expansion board on gpios?

Note: There would be additional power source than MCP2025. It is only 70MA and dissapears if there is no signal.

http://ww1.microchip.com/downloads/en/D ... 22306A.pdf
Attachments
linbus.png
linbus.png (15.96 KiB) Viewed 2320 times

mbt28
Posts: 29
Joined: Wed Feb 04, 2015 10:35 am

Re: Raspberry Pi IBUS and Powering

Fri Feb 06, 2015 3:33 pm

Since MCP2025 uses parallel method to communicate it is not possible to directly connect these ports. Here I made another scheme to simplify the logic. Feel free to comment on it.

Vreg output from MCP2025 triggers the Timer circuit based on 555, there would be a potans to adjust it, I am thinking on something between 3mins to 10mins. While MCP2025 sleeping, system doesn't use any power at all.
Attachments
rpi_cd_changer.png
rpi_cd_changer.png (24.54 KiB) Viewed 2298 times

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