Tips on Son's Notebook

Tutorial on Kicad, Solidworks for Quick Prototyping

Wed, 24 Dec 2025 00:00:00 +0000

Hello, fellow students! I’m Son, a beginner in KiCad and SolidWorks. The steps below will help you get familiar with KiCad or SolidWorks quickly. I hope that after following these basic steps, you’ll be able to start building simple prototypes.

Final Product#

Kicad#

Requirement#

First, we need to define what we’re designing. Our goal is to create a fuse box for voltage sense lines.

We have a total of 11 sense lines, and each one must have a fuse to protect the end device or downstream device. Our device can handle up to 300mA at peak, so choosing a 500mA fuse seems like a good option.

Things I wish I knew working on a research paper

Thu, 02 Apr 2026 00:00:00 +0000

Hi community fellows. This note is based on my experience. And I hope it will save you time working on a research paper for the first time. In this note, I will show how I organize files and folders to make a research more systematic.

Date: 4/2/2026
Revision: 4/2/2026

Survey ( or review)#

The purpose of a research is to find something new or make an improvement on existing thing. To do so we need to review existing works.

Build hugo site with github page

Sat, 04 Jul 2026 00:00:00 +0000

The reason I want to move to Hugo is because it is more modern and flexible compared to my Jekyll site.

The instruction is quite clear on their site https://gohugo.io/host-and-deploy/host-on-github-pages/

First, as always we need to create a github repo, and clone it in our local machine.

Next, we will need to create a Hugo project. I’m using Windows so I will select Extended-edition here. To access PowerShell, from command prompt we can type pwsh

English Connectives

Thu, 04 May 2023 00:00:00 +0000

After many hours of googling, mermaid is finally run on Github Page, thanks to Jojozhuang. I may not write another note for mermaid so I put the info here.

First, we need to add mermaid: true into our post layout. Second, we need to use div tag as below.

<!--
 to use mermaid in Jekyll we need to wrap it with <div>
-->
<div class="mermaid">
 your_mermaid_chart
</div>

Note: this tutorial is for Jekyll. Currently, this site is ran on Hugo with Book theme. For this theme, we only need to add fenced code blocks:

Explaining TCP flows

Fri, 27 Aug 2021 00:00:00 +0000

A few days ago, I wrote a note detailing how to set up a simple TCP client and server using netcat. Today, I have taken things a step further by capturing packets in Wireshark and providing a step-by-step explanation of how the TCP flow works. In the table below, you can find a general overview of this process.

Flow	Packet captured from Wireshark	Explaination
client -[SYN]-> server	Transmission Control Protocol, Src Port: 24491, Dst Port: 5000, Seq: 0, Len: 0 Source Port: 24491 Destination Port: 5000 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 0 (relative sequence number) Sequence Number (raw): 4126488336 [Next Sequence Number: 1 (relative sequence number)] Acknowledgment Number: 0 Acknowledgment number (raw): 0 1000 …. = Header Length: 32 bytes (8) Flags: 0x002 (SYN) Window: 65535 [Calculated window size: 65535] Checksum: 0xd6b0 [unverified] [Checksum Status: Unverified] Urgent Pointer: 0	First, client says “hi there, I’d like to connect, here is my number xxxxxxx36 “When client send a SYN packet to server. Wireshark will show you the relative sequence, or ACK number which is 0. But actually, it is a random number .
client <-[SYN,ACK]- server	Transmission Control Protocol, Src Port: 5000, Dst Port: 24491, Seq: 0, Ack: 1, Len: 0 Source Port: 5000 Destination Port: 24491 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 0 (relative sequence number) Sequence Number (raw): 547479085 [Next Sequence Number: 1 (relative sequence number)] Acknowledgment Number: 1 (relative ack number) Acknowledgment number (raw): 4126488337 1000 …. = Header Length: 32 bytes (8) Flags: 0x012 (SYN, ACK) Window: 65535 [Calculated window size: 65535] Checksum: 0xd7d0 [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 Options: (12 bytes), Maximum segment size, No-Operation (NOP), Window scale, No-Operation (NOP), No-Operation (NOP), SACK permitted [SEQ/ACK analysis] [Timestamps]	Server responses “oh sure, I’ve received your number xxxxxxx36. And I add one to keep track, so now it is xxxxxxx37. Please take my number xxxxxxx85 “After received the packet from client, server will send its own Sequence number 547479085 and Ackowledgement number.The Acknowledge number is the client’s Sequence number + 1 which is 4126488337
client -[ACK]-> server	Transmission Control Protocol, Src Port: 24491, Dst Port: 5000, Seq: 1, Ack: 1, Len: 0 Source Port: 24491 Destination Port: 5000 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 1 (relative sequence number) Sequence Number (raw): 4126488337 [Next Sequence Number: 1 (relative sequence number)] Acknowledgment Number: 1 (relative ack number) Acknowledgment number (raw): 547479086 0101 …. = Header Length: 20 bytes (5) Flags: 0x010 (ACK) Window: 10233 [Calculated window size: 2619648] [Window size scaling factor: 256] Checksum: 0xeace [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 [SEQ/ACK analysis] [Timestamps]	Client responses “I’ve received your number xxxxxxx85. And I add one to keep track, so now it is xxxxxxx86. We are synced”Client verifies receiving packet from the server by sending ACK (acknowledge) message. The ACK number is server’s Squence number + 1, 547479086
client -[PSH,ACK]-> server	Transmission Control Protocol, Src Port: 24491, Dst Port: 5000, Seq: 1, Ack: 1, Len: 34 Source Port: 24491 Destination Port: 5000 [Stream index: 0] [TCP Segment Len: 34] Sequence Number: 1 (relative sequence number) Sequence Number (raw): 4126488337 [Next Sequence Number: 35 (relative sequence number)] Acknowledgment Number: 1 (relative ack number) Acknowledgment number (raw): 547479086 0101 …. = Header Length: 20 bytes (5) Flags: 0x018 (PSH, ACK) Window: 10233 [Calculated window size: 2619648] [Window size scaling factor: 256] Checksum: 0xd07d [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 [SEQ/ACK analysis] [Timestamps] TCP payload (34 bytes)Data (34 bytes)	Now, client starts sending messages with flag PSH meaning “I have packed all the good stuffs, please send it imediately” Also, Next Sequence Number is expected to be 35 because it is sending out 34 bytes payload. ACK number is still 547479086 because it has not received anything from server
client <-[ACK]- server	Transmission Control Protocol, Src Port: 5000, Dst Port: 24491, Seq: 1, Ack: 35, Len: 0 Source Port: 5000 Destination Port: 24491 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 1 (relative sequence number) Sequence Number (raw): 547479086 [Next Sequence Number: 1 (relative sequence number)] Acknowledgment Number: 35 (relative ack number) Acknowledgment number (raw): 4126488371 0101 …. = Header Length: 20 bytes (5) Flags: 0x010 (ACK) Window: 10233 [Calculated window size: 2619648] [Window size scaling factor: 256] Checksum: 0xeaac [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 [SEQ/ACK analysis] [Timestamps]	After receiving the packet, server sends the ACK with previous ACK payload size (34). 4126488337 + 34 = 4126488371
client -[FIN,ACK]-> server	Transmission Control Protocol, Src Port: 24491, Dst Port: 5000, Seq: 35, Ack: 1, Len: 0 Source Port: 24491 Destination Port: 5000 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 35 (relative sequence number) Sequence Number (raw): 4126488371 [Next Sequence Number: 36 (relative sequence number)] Acknowledgment Number: 1 (relative ack number) Acknowledgment number (raw): 547479086 0101 …. = Header Length: 20 bytes (5) Flags: 0x011 (FIN, ACK) Window: 10233 [Calculated window size: 2619648] [Window size scaling factor: 256] Checksum: 0xeaab [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 [Timestamps]	After sending a note, client terminal is close, so it sends FIN (finish?) and ACK to server. At this time, both Sequence number and ACK number are the same as the above because server did not send anything.
client <-[ACK]- server	Transmission Control Protocol, Src Port: 5000, Dst Port: 24491, Seq: 1, Ack: 36, Len: 0 Source Port: 5000 Destination Port: 24491 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 1 (relative sequence number) Sequence Number (raw): 547479086 [Next Sequence Number: 1 (relative sequence number)] Acknowledgment Number: 36 (relative ack number) Acknowledgment number (raw): 4126488372 0101 …. = Header Length: 20 bytes (5) Flags: 0x010 (ACK) Window: 10233 [Calculated window size: 2619648] [Window size scaling factor: 256] Checksum: 0xeaab [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 [SEQ/ACK analysis] [Timestamps]	After receiving the FIN flag, server response with an ACK message + 1.
client <-[FIN,ACK]- server	Transmission Control Protocol, Src Port: 5000, Dst Port: 24491, Seq: 1, Ack: 36, Len: 0 Source Port: 5000 Destination Port: 24491 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 1 (relative sequence number) Sequence Number (raw): 547479086 [Next Sequence Number: 2 (relative sequence number)] Acknowledgment Number: 36 (relative ack number) Acknowledgment number (raw): 4126488372 0101 …. = Header Length: 20 bytes (5) Flags: 0x011 (FIN, ACK) Window: 10233 [Calculated window size: 2619648] [Window size scaling factor: 256] Checksum: 0xeaaa [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 [Timestamps]	Now, server closes its portal “hey client, I’m done with you”. Notice, Seq, and ACK are the same as above because server has not received anything from client.c
client -[ACK]- >server	Transmission Control Protocol, Src Port: 24491, Dst Port: 5000, Seq: 36, Ack: 2, Len: 0 Source Port: 24491 Destination Port: 5000 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 36 (relative sequence number) Sequence Number (raw): 4126488372 [Next Sequence Number: 36 (relative sequence number)] Acknowledgment Number: 2 (relative ack number) Acknowledgment number (raw): 547479087 0101 …. = Header Length: 20 bytes (5) Flags: 0x010 (ACK) Window: 10233 [Calculated window size: 2619648] [Window size scaling factor: 256] Checksum: 0xeaaa [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 [SEQ/ACK analysis] [Timestamps]	“Okay server, I have received your farewell letter so I will increase the ACK # to one “. Let reverse engineering, Client’s seq:36, in which we know it has sent 1 byte for SYN, 1 byte for FIN, and the rest are the payload. Client’s ack:2 shows us that it received 1 SYN and 1 FIN from server Also, Server’s seq:1 means it has sent 1 byte for SYN, and probally closes. That is why we don’t see the 2 seq. Server’s ack:36 shows that clent sent 1 SYN, 1 FIN, and 34 bytes of payload.

Quick Note - Decibel dB vs dBm

Tue, 24 Aug 2021 00:00:00 +0000

Many of us have heard about decibel unit in our daily lives, as it can be used to describe the loudness of our speakers, the strength of our antennas, or the signal strength from a transceiver. But what exactly are decibels (dB) and dBm? In this discussion, let’s explore these concepts and expand our understanding.

Explanation#

Deci-bel is ten time of a Bel (10 x Bel)
Bel is named after an inventor Alexander Graham Bell, in Bell Lab.
It is an unit of a ratio on base 10 logarithm scale
Bel is defined as $$X = \log\frac{P2}{P1} $$

TCP/UDP Flow Analysis with Wireshark and Windows Subsystem for Linux

Fri, 20 Aug 2021 00:00:00 +0000

During many of my interviews, I have been asked whether I understood TCP and UDP, and how they differed from each other. While I knew that TCP had an error-checking procedure that made the protocol more reliable but slower than UDP, my understanding was limited. Although I had learned about the detailed structure of these protocols in school, I didn’t have a chance to get hands-on experience with them. However, I later discovered an easy way to explore TCP and UDP packets using Windows Subsystem for Linux (WSL) and WireShark. As a result, I would like to share what I have learned today.