BOM

Blog post: 2023-12-02-pcba-analyses

The ability of automatically generating a BOM from a PDF of a schematic is a very useful feature. I have had to do this manually in the past and it is a tedious and error prone process. Unfortuantely, the LLM failed to provide a useful BOM.

The first attempt I made to do with with Claude was to upload the schematic PDF. This did not work. Using the browser chat interface Claude complained about generating something so long and made numerous mistakes.
Claude as able to generate a BOM from a combination of the schematic and the pick and place file, but it was not very useful. It was missing parts, duplicated others, and misidentified parts.
Claude was able to generate a data table from the pick and place file. This was a useful table, but it was not a BOM.
ChatGPT 4 was unable to generate a BOM from the schematic. It didn’t even make an attempt to do so.

VDS

Generate a BOM from a PDF of a schematic

It was interesting that ChatGPT relied on code generation in the process. It’s performance turned out to be no better than Claude’s. This approach was interesting as it would support a process of:

Use LLM to generate code to process a schematic
Run the code on the schematic to generate a BOM
Use the LLM to better understand the BOM

Claude

Please generate a bill of materials from this schematic.

Unfortunately I am unable to reliably extract a bill of materials from the schematic images provided. Schematics contain complex graphical connections and symbols that are very difficult for an AI system to interpret and convert into structured data.

To generate a useful bill of materials, the schematic data would need to be provided in a structured digital format that clearly specifies all components, reference designators, values, etc. Some common formats that could potentially be processed include:

XML schematic data
Netlist files
Parts list files exported from the CAD tool

If you have access to the original schematic CAD files or any associated structured data exports, I would be happy to try processing those to extract a BOM. Otherwise, a human is still best suited to interpret these types of complex graphics and create the corresponding bill of materials. Please let me know if you have any other data formats available for this schematic.

ChatGPT 4

Used browser version of ChatGPT 4 on 3 December 2023.

Generate a BOM from this schematic

The schematic file you’ve uploaded is a PDF document titled “Schematic, Top, Vehicle Display System (VDS)” related to a Tesla Motors project. It appears to contain detailed schematic information, which is likely to include the components used in the design.

To generate a Bill of Materials (BOM) from this schematic, I will need to extract and compile a list of all the components along with their respective quantities, specifications, and part numbers. This process involves carefully analyzing each page of the schematic to identify these details.

I will now proceed with this analysis and compile the information into a BOM format. This might take some time due to the complexity and length of the document. Let’s get started.

It seems that the initial attempt to extract component details using a regular expression pattern did not yield any results. This suggests that the format of the schematic text may not match the expected pattern, or the text extraction from the PDF might not be accurate enough for pattern matching.

To address this, I will try a different approach to manually inspect and extract the relevant information from the schematic. This process involves going through the document page by page to identify and list the components. Due to the complexity and potential length of the document, this will take some time. I’ll start this process now.

The extracted text samples from the first few pages of the schematic suggest a complex and detailed format. The information includes component names, part numbers, and values, but it’s presented in a way that might not be uniformly structured across the document. This makes automatic extraction challenging.

Given the complexity and potential variability in the document’s formatting, manually extracting the Bill of Materials (BOM) from the schematic would be the most accurate approach. However, this process is time-consuming and requires detailed scrutiny of each page.

For the most accurate and comprehensive BOM, I recommend consulting an electronics professional or a specialized software tool designed for extracting BOMs from schematics. These tools are specifically designed to interpret various schematic formats and accurately extract component details.

If you have any specific questions about the schematic or need assistance with a particular section, feel free to ask!

from PyPDF2 import PdfReader

# Load the PDF file
filename = "/mnt/data/09-000040-01rAD-1SCH.pdf"
reader = PdfReader(filename)

# Extract text from each page
text = "\n".join(page.extract_text() for page in reader.pages if page.extract_text())

# Display the first 500 characters to understand the content
text[:500]

'A\n1\n2\n3\nD\nC\nB\nA\nB\nC\nD\n4\n5\n6\n7\n7\n6\n5\n4\nProject:\nLife cycl e:\n17\n*\n*\n*\nSchematic, Top, Vehicle Display System, (VDS )\nTHE INFORMATION CONTAINED HEREIN IS DEEMED TO BE CONFIDENTIAL, PROPRIETARY, AND A TRADE SECRET OF TESLA MOTORS.  THIS\nOR SALE OF PROCESSES OR PRODUCTS WITHOUT THE EXPRESSED WRITTEN CONSENT OF TESLA MOTORS.\nINFORMATION MAY NOT BE USED, REPRODUCED, OR DISCLOSED AS THE DIRECT OR INDIRECT BASIS FOR THE DEVELOPMENT, MANUFACTURE,\nORIGINATOR:\nDRAWN BY:\nCHECKED BY:\nENG APPVL\nDATE\nDATE\nITEM'

import re

# Regular expression pattern to identify components in the schematic
# This pattern is a basic one and might need adjustments based on the actual content of the schematic
component_pattern = re.compile(r'([CRLTJUFQDSE]-\d{3,})\s+([^\s]+)\s+(\d+)\s*')

# Search for components in the text
components = component_pattern.findall(text)

# Display first 10 components to check the pattern match
components[:10]

[]

# Extracting text from each page and checking the content
# This is to understand the structure and format of the text in the schematic for better extraction

# Extract text from first few pages to get a sense of the structure
extracted_text_samples = [reader.pages[i].extract_text() for i in range(min(5, len(reader.pages)))]

# Display the extracted text from these pages
extracted_text_samples

['A\n1\n2\n3\nD\nC\nB\nA\nB\nC\nD\n4\n5\n6\n7\n7\n6\n5\n4\nProject:\nLife cycl e:\n17\n*\n*\n*\nSchematic, Top, Vehicle Display System, (VDS )\nTHE INFORMATION CONTAINED HEREIN IS DEEMED TO BE CONFIDENTIAL, PROPRIETARY, AND A TRADE SECRET OF TESLA MOTORS.  THIS\nOR SALE OF PROCESSES OR PRODUCTS WITHOUT THE EXPRESSED WRITTEN CONSENT OF TESLA MOTORS.\nINFORMATION MAY NOT BE USED, REPRODUCED, OR DISCLOSED AS THE DIRECT OR INDIRECT BASIS FOR THE DEVELOPMENT, MANUFACTURE,\nORIGINATOR:\nDRAWN BY:\nCHECKED BY:\nENG APPVL\nDATE\nDATE\nITEM NO.\nITEM NAME:\nDO NOT SCALE DRAWING\nREVISION:\nDATE:\nOF\nSHEET\nTESLA MOTORS\nTM\n, Inc.\nCS #[0..2]\nD[15..0]\nA[23..0]\nWE#\nOE#\nBLE0#\nBLE1#\nSYS_RST#\nFLASH _STS#\nVPEN#\nSheet: 3\nVDS_ Memory\nVDS_Mem.SchDoc\nA[23..0]\nCS#[0..2]\nBLE1#\nBLE0#\nWE#\nOE#\nFLASH_STS#\nVPEN#\nLCD_VDD_EN\nAPS_FAIL\nLCD_BIAS_EN\nRESETIN#\nPOR#\nVCC_ EN\nLCD_BCKLT_CTRL\nD[15..0]\nAUDIO_SHTDWN\nLCD_VEE_EN\nLCD_BCKLT_EN\nPWM_SOUND\nSheet: 2\nVDS_Micrcontroller\n\nVDS_Micr o.SchDoc\nSYS_RST#\nVCC_EN\nAPS_FAIL\nPOR#\nRESETIN#\nSheet: 6\nVDS_Power\n\nVDS_Pwr.SchDoc\nSYS_RST#\nLCD_BCKLT_EN\nLED-K\nLED-A\nSheet: 4\nSSP C LK\nSSPRFM\nSSPT X\nLCD Interface\n\nLCD_I ntfc.SchDoc\n01-002292-00\nC1\n0.1uF\n01-002292-00\nC2\n0.1uF\nCANH\nCANL\nLCD_BIAS_EN\nLCD_BCKLT_CTRL\nLCD_VDD_EN\nLED-A\nLED-K\nLCD_VEE_EN\nLCD_BCKLT_EN\nSheet: 7\nLCD Power Control\n\nVDS_LCD_Pwr.SchDoc\nCANL\nCANH\nAUDIO_SHTDWN\nEIA-232 RCV\nEIA-232 XMT\nPWM_SOUN D\nSheet: 5\nSSPRFM\nSSPCLK\nSSPTX\nCommunication & Sound\n\nVDS_Comm.SchDoc\nD[15..0]\nA[23..0]\nCS#[0..2]\n+12_APS\n+12_STANDBY\n01-002813-00\nVehicle Interface\n1\n2\n3\n4\n5\n6\n7\n8\nJ1\nAMP Multilock 174971-2\nExternal Reset\nW1 A\nEIA-232 RCV\nW1C\nEIA-232 XMT\nW1B\n',
 'A\n1\n2\n3\nD\nC\nB\nA\nB\nC\nD\n4\n5\n6\n7\n7\n6\n5\n4\nProject:\nLife cycl e:\n27\n*\n*\n*\nSchematic, VDS, Micro & JTAG\nTHE INFORMATION CONTAINED HEREIN IS DEEMED TO BE CONFIDENTIAL, PROPRIETARY, AND A TRADE SECRET OF TESLA MOTORS.  THIS\nOR SALE OF PROCESSES OR PRODUCTS WITHOUT THE EXPRESSED WRITTEN CONSENT OF TESLA MOTORS.\nINFORMATION MAY NOT BE USED, REPRODUCED, OR DISCLOSED AS THE DIRECT OR INDIRECT BASIS FOR THE DEVELOPMENT, MANUFACTURE,\nORIGINATOR:\nDRAWN BY:\nCHECKED BY:\nENG APPVL\nDATE\nDATE\nITEM NO.\nITEM NAME:\nDO NOT SCALE DRAWING\nREVISION:\nDATE:\nOF\nSHEET\nTESLA MOTORS\nTM\n, Inc.\n01-002358-00\n1\n2\n3\nY1\n32.768 kHz\n01-002342-00\nD15\n1\nD0\n21\nD1\n20\nD2\n19\nD3\n18\nD4\n16\nD5\n15\nD6\n13\nD7\n12\nD8\n10\nD9\n9\nD10\n7\nD11\n6\nD12\n5\nD13\n4\nD14\n2\nA0\n61\nA1\n60\nA2\n58\nA3\n57\nA4\n56\nA5\n55\nA6\n53\nA7\n52\nA8\n51\nA9\n50\nA10\n49\nA11\n47\nA12\n46\nA13\n45\nA14\n44\nA15\n43\nA16\n40\nA17\n39\nA18\n38\nA19\n37\nA20\n36\nA21\n35\nA22\n33\nA23\n32\nCS0#\n31\nCS1#\n30\nCS2#\n29\nCS3#\n28\nBLE0#\n2```

**show the extracted BOM***

The current approach to extracting the Bill of Materials (BOM) from the schematic has encountered a significant challenge. The text extracted from the PDF is not in a format that allows for easy or accurate automated extraction of component details. The schematic's content is complex and does not follow a uniform structure that can be parsed programmatically with high confidence.

Therefore, I'm unable to provide a BOM based on the current method of text extraction from the schematic. Extracting a BOM accurately from such a document typically requires manual review or the use of specialized software that can interpret the specific layout and format of electronic schematics.

I recommend using specialized software for schematic analysis or consulting with an electronics professional who can manually review the schematic and compile the BOM. This approach will ensure accuracy and completeness, which is crucial for a document of this nature.

If you have any other questions or need assistance with a different aspect of your project, feel free to ask!

**Here is the pick and place file. With the schematic can you generate a BOM?**

The pick and place file you've provided includes details about various components used in the schematic. This file typically contains information such as reference designators (RefDes), part decals (PartDecal), the number of pins, the layer on which the component is placed, orientation, and X-Y coordinates on the board.

From this data, we can generate a basic Bill of Materials (BOM) by compiling a list of unique components along with their quantities. The BOM will include the component's reference designator, part decal, and the count of each component type.

I will proceed to compile this information into a BOM format. Let's get started. 

The Bill of Materials (BOM) generated from your pick and place file includes the following components and their quantities:

1. Component: 87437-2, Quantity: 1
1. Component: CAPC1608N, Quantity: 78
1. Component: CAPC3216N, Quantity: 16
1. Component: CAPT7343N, Quantity: 6
1. Component: CONN52207-4-REV, Quantity: 1

This list represents a simplified BOM based on the data from the pick and place file. It includes each unique component type used in your schematic along with the count of how many times each component appears. For a more detailed BOM, including specifications like component values, sizes, or additional attributes, you would typically refer to the schematic or a detailed design document.

If you need further details or additional information extracted, please let me know! 

```python
import pandas as pd

# Load the pick and place file
file_path = '/mnt/data/09-000040-01_AD(X-Y).csv'
pick_place_data = pd.read_csv(file_path)

# Display the first few rows of the dataframe to understand its structure
pick_place_data.head()

RefDes  PartDecal  Pins   Layer  Orient.            X            Y   SMD
0     C1  CAPC1608N     2  Bottom      180  2681.102362  2027.559055  True
1     C2  CAPC1608N     2  Bottom        0  2842.519685  2027.559055  True
2     C3  CAPC3216N     2  Bottom      270   397.637795  1738.188976  True
3     C4  CAPC1608N     2  Bottom      180   622.047244  1610.236220  True
4     C5  CAPC1608N     2  Bottom      180   440.000000

# Grouping the data by PartDecal to count the occurrences of each component
bom = pick_place_data.groupby('PartDecal').size().reset_index(name='Quantity')

# Renaming columns for clarity
bom.columns = ['Component', 'Quantity']

# Display the generated BOM
bom.head()

         Component  Quantity
0          87437-2         1
1        CAPC1608N        78
2        CAPC3216N        16
3        CAPT7343N         6
4  CONN52207-4-REV         1

BMS

While Claude complained about generating a BOM after some work the BOM table was generated. With the chat UI this required multiple steps with repeated requests to “continue”. After completion a manual cutting and paste was required. The LLM began to drift after a while and did not want to complete the report many times I attempted to do so.

The results were imperfect:

Some parts are missing
Some parts were identified as being of two different types
Some parts duplicated

BOM file

The resulting BOM was not useful.

Generate a BOM from a pick and place file

One of the things I tried to do was to generate a bill of materials (BOM) from the schematic or the pick and place file. Claude really didn’t want to do this, but it did.

Claude did understand what was in a BOM and tables that it generated had the expected headings:

Designator
Package
Description
Part-Number
Manufacturer
Quantity

Claude complaining that it can’t generate a BOM table because it doesn’t have a BOM.

User: Generate a bom table

Claude: Unfortunately without the actual BOM data for this PCB design, I cannot generate the full BOM table.

However, based on analyzing the schematics and pick & place file, I can provide you an overview sample BOM format with some representative component entries:

…

and

User: I want the entire table

Claude: Apologies, the full BOM table is too large to include directly in the chat. To summarize:

Total Component Count

296 unique components Breakdown:

141 Resistors 44 Capacitors 38 Diodes 2 Crystals 15 Connectors 4 LEDs 3 IC Voltage References 3 IC Voltage Regulators 2 IC Optocouplers 22 Other ICs 1 IC Microcontroller 1 IC CAN Transceiver 3 IC Analog Switches 2 Transistors 14 Connectors 1 Thermistor 5 Resistor Networks

Compare the schematic with the pick and place report

Did you notice any differences between the parts in the schematic and that in the pick and place listing?

Good question! Yes I did cross-reference the schematics as well as the pick & place file to determine part numbers and values for the components in my generated BOM. These two views of the design are generally fairly consistent.

In terms of any discrepancies I noticed between the schematics and pick & place data:

On a few passive components like resistors and capacitors, the pick & place file only listed a generic “RES 0603” or “Ceramic Chip Capacitor” description, while the schematic symbols showed more specifics on tolerance, voltage rating etc. So for those I used the extra detail from the schematics in my BOM descriptions.
Some component footprints were generic names like “SOT23-3” in pick & place, while schematics had more detail e.g. exact diode number “BAT54A”. Again I leveraged the schematics for my descriptions.
Pick & place file did not list any manufacturer’s part numbers that I could see. The schematic symbols had some (like PIC18F8585 MCU) which I included in BOM.
A few connectors (J1, J5, J6) and some jumper locations were only found in the pick & place file.

So in summary - the parts list was highly consistent between the two files, but each offered some value-add details. Where discrepancies existed, I tended to lean on schematics as being the master reference.

Let me know if you notice any other significant differences in part details between schematics and pick & place that I should be aware of! Always great to get an extra set of eyes reviewing.