Fix technical inaccuracies in protocol data rates, type casts, and component descriptions by Copilot · Pull Request #224 · circuits-and-code/circuits-and-code-book

Copilot · 2025-11-28T02:45:51Z

Audit of book content identified several technical inaccuracies that could mislead readers.

Protocol Data Rates (signalling.tex)

Fixed I2C expansion: "Inter-Interconnected Controller" → "Inter-Integrated Circuit"
Fixed UART units: 115.2 kHz → 115.2 kbps (bit rates, not frequency)
Standardized capitalization: mbps → Mbps

Code Example Type Mismatch (keyword.tex)

// Before: type mismatch in cast
volatile const uint8_t* const REG = (uint32_t*)0x12345678;

// After: consistent types
volatile const uint8_t* const REG = (uint8_t*)0x12345678;

Oscilloscope Probe Description (oscilloscope.tex)

Corrected: 10x probe attenuates (divides) voltage by 10, not "scales" by 10

Semaphore Semantics (mutex_vs_semaphore.tex)

Fixed wait operation: blocks when count == 0, not "less than zero" (counting semaphores are non-negative)

LDO Pass Element (buck_vs_ldo.tex)

Corrected transistor type: "PMOS FET or NPN BJT" → "PMOS FET or PNP BJT" (PNP provides lower dropout)

Original prompt

This section details on the original issue you should resolve

<issue_title>Audit and review the book for any technical inaccuracies</issue_title>
<issue_description>Look through the book source and find any technical inaccuracies. Suggest changes to improve the correctness of such inaccuracies. Goal is to make sure that no incorrect knowledge is distributed by means of the book</issue_description>

<agent_instructions>Crosscheck all technical assertions with online sources where applicable</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes Audit and review the book for any technical inaccuracies #223

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…x/semaphore, and buck/LDO sections Co-authored-by: sahil-kale <32375512+sahil-kale@users.noreply.github.com>

sahil-kale · 2025-11-28T02:54:25Z


 \subsubsection{Losses}
-In an LDO, the pass element transistor (usually implemented as a PMOS FET or NPN BJT) acting similarly to a variable resistor is actively controlled to maintain a fixed output voltage, regardless of changes to input voltage, load current, and temperature. This variable resistance gives rise to \textit{conduction losses} within this type of regulator. Assuming a fixed input voltage and load current, the power losses in an LDO can be calculated as $P = V_{drop} \cdot I_{out} = (V_{in} - V_{out}) \cdot I_{out}$. Note that the power is dissipated as heat in the pass element - this is why LDOs are often equipped with a heat sink, and attention may be required to the thermal limitations of the chosen LDO. \newline
+In an LDO, the pass element transistor (commonly implemented as a PMOS FET or PNP BJT for low dropout performance) acting similarly to a variable resistor is actively controlled to maintain a fixed output voltage, regardless of changes to input voltage, load current, and temperature. This variable resistance gives rise to \textit{conduction losses} within this type of regulator. Assuming a fixed input voltage and load current, the power losses in an LDO can be calculated as $P = V_{drop} \cdot I_{out} = (V_{in} - V_{out}) \cdot I_{out}$. Note that the power is dissipated as heat in the pass element - this is why LDOs are often equipped with a heat sink, and attention may be required to the thermal limitations of the chosen LDO. \newline


@DanielJPuratich is this legit?

wow yea copilot is good. might be worth dropping the mention of BJTs at all or even this parenthesized comment entirely, seems like modern LDOs are entirely PMOS FETs? Googling around.

aight imma yolo merge this for now

sahil-kale · 2025-12-02T02:26:48Z

 #include <stdint.h>

-volatile const uint8_t* const UART_RECEIVE_REGISTER_READ_ONLY = (uint32_t*)0x12345678;
+volatile const uint8_t* const UART_RECEIVE_REGISTER_READ_ONLY = (uint8_t*)0x12345678;


how tf did my very strict compiler warnings not ding this :/

Copilot

Pull request overview

This PR corrects several technical inaccuracies across documentation files, addressing protocol specifications, type safety, and component descriptions. While most corrections are accurate, there are critical issues with the I2C and SPI data rate unit changes that introduce new inaccuracies.

Key changes:

Corrected I2C expansion, UART bit rates, and CAN capitalization in protocol table
Fixed type cast mismatch in const keyword example
Improved oscilloscope probe and semaphore operation descriptions
Corrected LDO transistor type from NPN to PNP

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/signalling.tex	Fixes I2C name expansion, UART units (kHz→kbps), and CAN capitalization; however, incorrectly changes I2C/SPI from Hz to bps
src/keyword.tex	Corrects type cast from uint32_t* to uint8_t* to match pointer type
src/oscilloscope.tex	Improves accuracy by changing "scales" to "attenuates" and clarifying voltage division
src/mutex_vs_semaphore.tex	Corrects semaphore wait operation description for non-negative count semantics
src/buck_vs_ldo.tex	Fixes LDO pass element transistor type from NPN to PNP BJT

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Copilot · 2025-12-05T00:37:44Z

-            & CAN & Controller Area Network & Differential Pair & Bus & Half-Duplex & Open Drain & Asynchronous & 1 mbps & 8 mbps \\ \hline
+            & UART & Universal Asynchronous Receiver Transmitter & Single Ended & Point to Point & Full-Duplex & Push Pull & Asynchronous & 115.2 kbps & 921.6 kbps \\ \hline
+            & I2C & Inter-Integrated Circuit & Single Ended & Bus & Half-Duplex & Open Drain & Synchronous & 400 kbps & 1 Mbps \\ \hline
+            & SPI & Serial Peripheral Interface & Single Ended & Bus & Full-Duplex & Push Pull & Synchronous & 24 Mbps & 60 Mbps \\ \hline


SPI data rates should be expressed in Hz (clock frequency), not bps (bit rate). SPI is a synchronous protocol that uses a clock signal (SCK/SCLK), and its speed is specified by the clock frequency.

Change "24 Mbps" to "24 MHz" and "60 Mbps" to "60 MHz".

Suggested change

& SPI & Serial Peripheral Interface & Single Ended & Bus & Full-Duplex & Push Pull & Synchronous & 24 Mbps & 60 Mbps \\ \hline

& SPI & Serial Peripheral Interface & Single Ended & Bus & Full-Duplex & Push Pull & Synchronous & 24 MHz & 60 MHz \\ \hline

Copilot · 2025-12-05T00:37:45Z

-            & SPI & Serial Peripheral Interface & Single Ended & Bus & Full-Duplex & Push Pull & Synchronous & 24 MHz & 60 MHz \\ \hline
-            & CAN & Controller Area Network & Differential Pair & Bus & Half-Duplex & Open Drain & Asynchronous & 1 mbps & 8 mbps \\ \hline
+            & UART & Universal Asynchronous Receiver Transmitter & Single Ended & Point to Point & Full-Duplex & Push Pull & Asynchronous & 115.2 kbps & 921.6 kbps \\ \hline
+            & I2C & Inter-Integrated Circuit & Single Ended & Bus & Half-Duplex & Open Drain & Synchronous & 400 kbps & 1 Mbps \\ \hline


I2C data rates should be expressed in Hz (clock frequency), not bps (bit rate). I2C is a synchronous protocol that uses a clock signal (SCL), and its speed is specified by the clock frequency.

The correct values should be:

Typical: 400 kHz (Fast mode)

Maximum: 1 MHz (Fast mode plus)

Change "400 kbps" back to "400 kHz" and "1 Mbps" to "1 MHz".

Suggested change

& I2C & Inter-Integrated Circuit & Single Ended & Bus & Half-Duplex & Open Drain & Synchronous & 400 kbps & 1 Mbps \\ \hline

& I2C & Inter-Integrated Circuit & Single Ended & Bus & Half-Duplex & Open Drain & Synchronous & 400 kHz & 1 MHz \\ \hline

Initial plan

0d39043

Copilot AI assigned Copilot and sahil-kale Nov 28, 2025

Copilot started work on behalf of sahil-kale November 28, 2025 02:46 View session

Fix technical inaccuracies in signalling, keyword, oscilloscope, mute…

bbe2ccb

…x/semaphore, and buck/LDO sections Co-authored-by: sahil-kale <32375512+sahil-kale@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Audit and review the book for technical inaccuracies~~ Fix technical inaccuracies in protocol data rates, type casts, and component descriptions Nov 28, 2025

Copilot AI requested a review from sahil-kale November 28, 2025 02:55

Copilot finished work on behalf of sahil-kale November 28, 2025 02:55

sahil-kale approved these changes Nov 28, 2025

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sahil-kale approved these changes Dec 2, 2025

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sahil-kale marked this pull request as ready for review December 5, 2025 00:35

Copilot AI review requested due to automatic review settings December 5, 2025 00:35

sahil-kale merged commit 262395c into main Dec 5, 2025
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Copilot finished reviewing on behalf of sahil-kale December 5, 2025 00:36

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Fix technical inaccuracies in protocol data rates, type casts, and component descriptions#224

Fix technical inaccuracies in protocol data rates, type casts, and component descriptions#224
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	& SPI & Serial Peripheral Interface & Single Ended & Bus & Full-Duplex & Push Pull & Synchronous & 24 Mbps & 60 Mbps \\ \hline
	& SPI & Serial Peripheral Interface & Single Ended & Bus & Full-Duplex & Push Pull & Synchronous & 24 MHz & 60 MHz \\ \hline

	& I2C & Inter-Integrated Circuit & Single Ended & Bus & Half-Duplex & Open Drain & Synchronous & 400 kbps & 1 Mbps \\ \hline
	& I2C & Inter-Integrated Circuit & Single Ended & Bus & Half-Duplex & Open Drain & Synchronous & 400 kHz & 1 MHz \\ \hline

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Protocol Data Rates (signalling.tex)

Code Example Type Mismatch (keyword.tex)

Oscilloscope Probe Description (oscilloscope.tex)

Semaphore Semantics (mutex_vs_semaphore.tex)

LDO Pass Element (buck_vs_ldo.tex)

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Copilot AI commented Nov 28, 2025 •

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