ECE 320 · Week 1
Modern Computer: Embedded Systems
Six boot stages, in order, and what a quoted log line is.
Week 1 of 10 · Das Frite
ECE 320 · Week 1
The board: Das Frite
- 5 V
- 3.3 V
- Ground
- GPIO
- I2C
- SPI
- UART
- PWM
- ADC
- I2S
- S/PDIF
- Clock
- SDIO
Colours as on the Das Frite pinout, where each pin's name is. The square pad is pin 1.
ECE 320 · Week 1 · In class
Six boot stages, in order, and what a quoted log line is.
- The order is the BootROM, the SRAM stage, DRAM, the bootloader, the kernel, and init.
- A quoted log line is a line you copy from your own capture and attach to one of those names.
- A login screenshot is not this week's work.
ECE 320 · Week 1 · In class
Capture one boot on the serial console from the section image.
- Mark the same six names on a second capture.
- The homework is one sentence of your own for each stage name, with no line copied from a log.
ECE 320 · Week 1 · Lecture
The header, by function
- Ground
- UART
Other pins are dimmed. Colours as on the Das Frite pinout, where each pin's name is. The square pad is pin 1.
ECE 320 · Week 1 · Lecture
Each stage makes the next one possible
- At power-on almost nothing works: no DRAM, no file system, no drivers.
- Each stage runs with what the one before it set up, and sets up a little more.
- The order is fixed: BootROM, SRAM stage, DRAM, bootloader, kernel, init.
- A stage that fails stops the chain, so the last stage that printed tells you where to look.
ECE 320 · Week 1 · Lecture
Where each stage runs
| Stage | Runs from |
|---|---|
| BootROM | mask ROM inside the SoC, fixed at manufacture |
| SRAM stage | small on-chip SRAM |
| DRAM | code in SRAM that sets up and trains the DRAM |
| Bootloader | DRAM |
| Kernel | DRAM |
| init | user space: the first process |
ECE 320 · Week 1 · Lecture
What a quoted log line is
- A line copied character for character from your own capture, not retyped and not from someone else's log.
- Attached to exactly one stage name.
- Chosen because it could only come from that stage, not because it is the first line you saw.
- Kept with the file it came from, so anyone can find it again.
ECE 320 · Week 1 · Lecture
Capturing the whole boot
- Open the serial terminal and start logging before applying power; the first stages print only once.
picocom -b 115200 --logfile boot1.log /dev/ttyUSB0shows the console and writes it to a file.- 115200 baud is the board's console rate. The adapter's device name is in
dmesgafter you plug it in. - Keep the raw file. Mark stages on a copy.
ECE 320 · Week 1 · Lab
Lab
- From the section image the TA wrote with the desktop imager, capture one boot log on the serial console.
- Mark six stages on it. Do not submit a login screenshot. Second pass: capture the log once more and mark the same six names.
- Assemble the lab hand-in: A stage map of one boot log naming the BootROM, the SRAM stage, DRAM, the bootloader, the kernel, and init, with one quoted line for each.
ECE 320 · Week 1 · Lab
Hand in
A stage map of one boot log naming the BootROM, the SRAM stage, DRAM, the bootloader, the kernel, and init, with one quoted line for each.
ECE 320 · Week 1 · Homework
Homework
- Write one sentence of your own for each of the six stage names, with no line copied from a log.
ECE 320 · Week 1 · Homework
Turn in
Those six sentences.
ECE 320 · Week 1 · Read
Read
On the lab site: Module 0, First boot, ends at capturing the log. This week grades the six named stages.
ECE 320 · Week 1 · Next
Week 2
Rail order on a supplied trace, and which regulator feeds the SoC.