Thursday 30 May 2013

Minix on the BeagleBone Black Part 3 - Booting

This is the third post in a 3 part mini-series on getting Minix up and running on the new BeagleBone Black. It's intended to help those interested in following my work over the summer. I'll be looking for people interested in helping test out my code as the summer goes along. In the previous posts, I described what hardware you'll need and how to cross build a Minix SD card image. In this post, I will go over terminal program setup, booting, and logging into Minix.

The first step is to take your MicroSD card and insert it into the MicroSD card slot on the bottom side of the board with the label facing up, pads facing down. Next, attach the FTDI USB-Serial Cable. Be sure you're using the 3.3V version of the cable, and also be sure that it's oriented correctly. Pin 1 is marked on the board with a white dot, it's closer to the ethernet connector than the MicroSD card slot. Pin 1 on the connector is marked with a small arrow and the insulator of the wire going to pin 1 should be black. Now plug the USB side of the USB-Serial cable into your computer. The driver should be loaded automatically. Use `dmesg` or `ls /dev/ttyUSB*` to see what device file to use in the next step. It will most likely be /dev/ttyUSB0 unless you have other USB to Serial adaptors plugged in. You can use pretty much any terminal program. I use picocom for no particular reason other than it is the first one I tried and it worked. Most programs have the proper default settings except for the baud rate which needs to be set to 115200 BAUD. Here's how to invoke picocom:

picocom -b 115200 /dev/ttyUSB0

The final step, once the terminal program is running, is to plug in the BeagleBone to a power supply. This should cause it to start booting. It will default to the MicroSD card and should start Minix automatically. Eventually, you'll be presented with a login prompt. The default login is "root" with no password. That will give you a shell where you can issue commands. As the project progresses, I'll be making posts explaining how to get started with i2c on Minix.

When you're done, you can issue the `halt` command. Minix will stop itself and print a message saying that it's okay to turn off the computer. At this point, you can remove the power supply and unplug the USB cable from your computer.

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