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Progress Report

A project log for Pi Chart

A wireless nautical chart plotter based on a Raspberry Pi and a sunlight readable screen.

Erland LewinErland Lewin 05/05/2016 at 22:290 Comments

Progress Report

It's been a while since the last log entry - I've been very busy both with work and advancing the project.

Raspberry Pi on/Off board

The Raspberry Pi On/Off board has been built, but it turned out that the USB plug did not have a good mechanical connection to the PCB board (I think it was designed to be molded in a plug). I can use the board anyway, but will need to solder a USB plug on a cable to the board, instead of plugging it directly into the Pi. I have not tested it thoroughly yet.

Pixel Qi Display

The driver board I got with the display must in some way be defective, because it draws way more current than specified. In a battery operated system, that's a big problem.

I bought an MT561-B VGA to LVDS board on E-bay. It works really well, doesn't get hot, and uses less power than the HDMI board that came with the Pixel Qi display. However, it needs VGA as input which the Pi doesn't have.

So, I designed a variant of Gert's VGA666 board which uses GPIO pins driven by the graphics processor with a resistor ladder DAC. My board allows any of the pixel formats, and by using the 888 RGB, but only the top 4 bits of the green color channel, I can still have two pins for the serial port to communicate with the nRF51822 bluetooth device and two extra GPIOs for sensing the power switch and something else. I've just ordered the VGA PCBs (from OSHPark, trying a new PCB manufacturing service).

Software

After struggling with the Linux bluetooth stack on the Raspberry Pi and a USB Bluetooth dongle, I decided to use the same nRF51822 board I use in the GPS dongle as an interface for the chart plotter. I've written software that communicates as a client to the GPS dongle software, and prints output to the serial port, which is read by the Raspberry Pi. Work remains, but I have a proof of concept that it works.

Solar Power for the Dongle

After realizing that the cheap, simple DC/DC buck converter I had intended to use was not sufficient for the GPS dongle, I designed my own version of Adafruit's Solar LiPo charger. I've received the PCBs (from Dirty PCBs, worked well), and have just ordered the components for it and the VGA board.

All the above has not been pushed to the Repos, let me know if you're interested in any information. If anyone wants unpopulated PCBs for the Raspberry Pi On/Off board, I could send them some for free (I have more than I'll need).

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