Bringup is Hard [pdf]

garbled.net

71 pointsbeefhash3 comments

My primary job for almost 2 years was bringing up boards. It is at the same time immensely challenging and absolutely unappreciated.

As an example of the challenge, My first task in the job was to port a ROM monitor to a custom StrongARM board. StrongARM had JTAG, but no run control, therefore, I could load and run code, but could not stop it or look at memory.

At first, I could only observe (with my eyes) when the board resets. Soon, I could toggle 4 LEDs on the board. That was enough for me to debug by streaming values one nybble at a time. Soon after, I could emit characters from the serial port.

That was the good old days.

Heh. For me, I used an IR thermometer to figure out when the board was running and when it quiesced. Thankfully most of the work was already done and I just needed to put some pieces together so I got a console shortly afterward. Then it was the normal development work of getting a more current kernel version running, etc.

One thing to watch out for is when the board manufacturer changes its memory map without telling you. Boards built before April booted and the new ones didn't. Fortunately, the product was still in the development stage.

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