Debugging

![](./img/debugging.jpg)

01-03-2021

Fab Academy 2021

???

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3. used cloned view for beam, share screen in zoom.

---

1. Attitude
2. General principles
3. Multimeter
4. Oscilloscope
5. Logical analyzers
6. Flashing your board
7. Serial (or any) "Hello world!"
8. In-circuit / On-Chip debugging
9. USB and computer detection
10. Radio Communications
11. How to debug almost anything kit

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class: center, middle, chapter

# Attitude

![](./img/attitude.jpg)

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class: middle, center

## ERROR

---

<p>
.image_right[
<img src="img/colombo1.jpg" height="600px">
]

## Write

<p>

- what is happening
- what is the environment
- what are you doing
- what are the results

---

## Read

---
class: middle,center
<img src="img/itruns.jpg" height="600px">

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# General principles

Where to start How to narrow down the source of the problem

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class: middle

## Narrowing down the problem
<P>
.image_right[
![](./img/oitwasatypo.jpg)
]

<p>

- always first do visual check
/
	- traces
	- solder
	- components

everything looks good but...

---

---

## It's not working

![](./img/fabtinyisp.jpg)

concentrate only on the relevant parts.

---

## you could not program the board

![](./img/fabtinyisp_isp-check.jpg)

big chance problem is located only here.

---

## programmed but not showing up.

![](./img/fabtinyisp_usb-check.jpg)

big chance problem is located only here.

---

## programmed, showing, no leds

![](./img/fabtinyisp_led-check.jpg)

big chance problem is located only here.

---

# Multimeter

- "Continuous" phenomenons
- Continuity check (+diodes orientation) : symbol
- Voltage/Power check : parallel measurement
- Resistance / current / ...

---

## Continuity

- Test power supply to power pins continuity
- Check fuses, diodes orientations, ...
- Check short-circuits
- Check traces

![](img/continuity.jpg)

---

## Voltage

- Parallel measurement => check your cables!
- ! absolute maximum ratings (may burn your component)
- Power supply impedence / max power, badly selected
- GND/VCC loop

---

## Power supply

- Nothing : open circuit, short circuit, line break, blown fuse, ...
- Voltage too low : power supply impedence, badly selected, ...
- Voltage too high : above max. ratings, dead zener/reg., ...
- GND/VCC loop

---

## How to check current, resistor, capacitor, ...

- Learn more about you mulimeter capabilites!
- Current : serie
- Resistor : parallel
- capacitor : parallel (+ polarity)

---

# Oscilloscope

- "Variable / random" phenomena
- Variable signals (analog, communications, blink, sound, ...)

---
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Fab Academy 2021 - recitation on debugging  </span></div>

## Oscilloscope (main functions)

- "Real" voltage levels, high sampling rate (> 10MHz - 1GHz)
- Dynamic view
- Triggers/Time/Level
- Lots of analysis capabilities inside (play with menus : capture/ analyse / freq-time / intervals / Peak-peak / frequency / ...)
- Few channels (~1-4)
- Expensive tool. Poor human alternative : sound card mic/line input [< 44.1kS/sec]

---

"Random" behaviours :
- Check proper signals
- Check proper power (stable enough?)
- DC decoupling capacitor? (same idea as toilet flush ;-) )

---

---

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---

# Logical analyzer

- Variable **digital** signals
- Communications [UART, I²C, SPI, 1-Wire, ...]
- PWM
- Clock
- ...

---

## Logical analyzers

- High sampling rates (> 100MHz - 500 MHz)
- Only "logical levels" (0 : <0.6V - 1 : > 1.2V => usually not CMOS logic!)
- Multiple channels (8-16...)
- "Unexpensive" (compared to oscilloscopes)
- Allows you to read complex protocols easily

[Saleae](https://www.saleae.com/), [Pulseview](https://sigrok.org/wiki/PulseView) with Cypress CY7C68013A, ...

---

# Flashing your board
And what can go wrong

## EDBG for flashing ARM (1)

- Connect a CMSIS-DAP SWD adapter
- 10-pin 1.27mm connectors are convenient, but triple check the orientation
- If VCC pin is unused, power your target device separately
- Make sure the programmer is on 3.3V if programming SAMD

## EDBG for flashing ARM (2)

- List programmers

```c
edbg -b -l
```

- Erase first (!) and load program

```c
edbg -b -e -p -v -t <processor> -f <program.bin>
```

- flags:
	- -b: verbose (optional)
	- -e: erase
	- -p: program
	- -v: verify (optional)
	- -t: target type (e.g. samd11)

- Common problems
	- Programmer not listed: check USB
	- Invalid response: check JTAG connection

## UPDI for Flashing AVR (1)

- All you need is a serial adapter
- RX and TX connected together with a 4.7k resistor
- VCC is optional but ensures both chips talk at the same logic level
- Programming is initiated with a break (LOW level for a long duration)

## UPDI for Flashing AVR (2)

- pymcuprog.py

```c
pymcuprog -d <processor> -t uart -u <port> -v info erase
pymcuprog -d <processor> -t uart -u <port> -v info write -f <program.hex>
```

- Arduino IDE
	- install megaTinyCore (ATtiny 1-series) or DxCore (AVR DA/DB)
	- use "serial port and 4.7k (pyupdi style)" programmer
	- select correct serial port and click upload

- Common problems
	- wrong serial settings: adapter needs 2 Stop bits and Even parity
	- "incorrect echo": are RX and TX connected together?
	- "UPDI initialisation failed": have you tried turning it off and on again?

---

# Serial (or any) "Hello world!"

Sending internal info through communication line

## Serial (or any) "Hello world!"

- Show any external signal on code execution (eg : LED blinking)
- Send register value or "hello world" message through communication lines (eg : serial/UART)
- Very simple to implement but requires functional microcontroller
- Allows you to follow execution steps

Example:
```c
#define DEBUG_MODE 1
...
#if DEBUG_MODE
  Serial.print("DEBUG -- MyVal value = ");
  Serial.println(MyVal, DEC);
#endif
```

---

# USB

Check your USB device can be found by the OS

## USB

.small[
```terminal
ndcoster@chr-40 ~ $ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 003: ID 046d:c05a Logitech, Inc. M90/M100 Optical Mouse
Bus 001 Device 004: ID 413c:2011 Dell Computer Corp. Multimedia Pro Keyboard
```
]

If nothing :
- Check lines, voltages ("5V" power BUT 3.3V communication D-/D+), zener orientations, ...

If declared but doesn't work :
- Check USB devices permissions
- Check firmware (inject a tried-and-tested)

---

# Radio Communications

How to see what you can't even touch?

## Radio communications

- Frequency ranges (~kHz to ~GHz)
- Use receiver modules
- DVB-T receiver as radio tool : [GNU Radio (live), SDR environment](https://wiki.gnuradio.org/index.php/GNU_Radio_Live_SDR_Environment)

---

# How to debug almost anything?

---
<div class="my-footer"><span>
<a rel="license" href="http://creativecommons.org/licenses/by-nc/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-nc/4.0/80x15.png" /></a></a>
Fabacademy 2020 - recitation on debugging  </span></div>

## Simple, smart and cheap

- workbench in a case
<center>
<img src="img/kit.jpg" width="300">
</center>
---
<div class="my-footer"><span>
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Fabacademy 2020 - recitation on debugging  </span></div>

## Logic Analyzer (24Mhz 8ch)

## t1614 Hello World
<br>
<hr>

## ts100 solder iron

## ts100 solder iron

## ts100 solder iron

<p>
<center>
<img src="img/ts100_batt.jpg" width="800">
</center>
</p>
---
<div class="my-footer"><span>
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Fabacademy 2020 - recitation on debugging  </span></div>

## DPS3005 Bench Power Supply

## DPS3005 Bench Power Supply

## Happy Debugging