2 layers36.1 × 21 mm
2 layers25.9 × 19.3 mm
Uart data logger
123swk123/uart_data_logger1UART data logger to SD card using CH32V003
- Size
- 25.9 × 19.3 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 14
- Nets
- 29
- Pads
- 65
- Tracks, vias
- 98, 8
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 3 Feb 2026
- Updated
- 1 Apr 2026
Overview
Uart data logger is an open-source printed circuit board by 123swk123, from the 123swk123/uart_data_logger repository on GitHub, published under the MIT licence. It is a 2-layer board of 25.9 × 19.3 mm with 14 parts on 29 nets, routed with 98 tracks and 8 vias.
It is built around the CH32V003F4P6 and AZ1117CH-3.3TRG1. Its parts include 5 capacitors, 4 connectors, 2 resistors, 2 ICs and 1 switch. It belongs with the interfaces and adapters and sensors and measurement boards and the RISC-V boards of this library.
Main components
2
CH32V003F4P6
TSSOP-20-175milTSSOP-20-175mil Microcontrollers (MCU/MPU/SOC) ROHSWCH (Nanjing Qinheng Microelectronics)Microcontrollers (MCU/MPU/SOC)
AZ1117CH-3.3TRG1
SOT-223-20℃~+125℃@(Tj) 0.003%Vout 1 1.2V@(800mA) 1.35A 10V 3.3V 4mA 70dB@(120Hz) Fixed Over Current Protection、Over Temperature Protection Positive SOT-223 Voltage Regulators - Linear, Low Drop Out (LDO) Regulators ROHSDiodes IncorporatedVoltage Regulators - Linear, Low Drop Out (LDO) Regulators
README
README.mdUART data logger to SD card
[!NOTE] Work in progress...
This is a simple UART data logger, logger saves the data to FAT(12/16/32) formatted SD card.
Schematic
Preparations
- Any SDHC card should work, but I have tested them upto 8GB
- Format the card as FAT12/16/32
- copy the config.txt and head to root of the SD card
How to use the logger
- After power-on the status LED will be OFF
- start/stop button is a simple toggle switch
- press once to start logging
- press again to stop logging
- Always remove the card when status LED is OFF.
| Status LED | Remarks |
|---|---|
| OFF | Logger stopped, free to remove the SD card after powering down |
| ON | Logger running, do not remove the card |
| Constant blinking | Logger error |
| Brief pulsing | Actively logging the received UART data |
config.txt
first 2 lines are comment and they are skipped during the configuration process
3rd line describes the serial port configuration.
s<no>:baud rate,data bits<8,9>,parity<0,1,2>,stop bits<1,2>,output formatter<c,d,x,X>,seq start char,seq end char
s<no>: Serial port number, starting from 1
range: 1 to Maximum no.of UART HW supported by the controller, in case of CH32V003 its just 1.
Example: s1baud rate: UART logger baud rate
range: 1200 ~ 300000 (check CH32v003 reference manual to calculate the percentage error due to divider round off)
Example: 115200data bits: UART logger data bits per frame
range: 8, 9
Example: 8parity: UART data partiy enable/disable
range: 0 - No parity (disabled)
1 - odd parity
2 - even parity
Example: 0stop bits: No.of stop bits per frame
range: 1, 2
Example: 1output formatter: logger output encode format
range: c - store the UART data in a transparent 8-bit ASCII raw
u - store the UART data as unsigned decimal value
x - store the UART data as hexadecimal value
X - store the UART data as hexadecimal value (all caps)
Example: xseq start char: a 9-bit unsigned integer. Upon reciving this character logger notes the event time stamp at start of the row/line
and the logger continues to log the sub-sequent received data in the same row/line as per the output format
Note: This seq start character will not be logged.
time stamp format: hour.minute.seconds.milli second (resolution: 100milli)
range: 0 ~ 511
Example: 13 (\r)seq stop char: a 9-bit unsigned integer. Upon reciving this character logger closes the current row/line with \r\n and
creates a new row/line, then the logger waits for seq start character.
Note: seq stop character will not be logged; Seq start and stop char can be the same.
range: 0 ~ 511
Example: 10 (\n)4th line describes the time offset information.
t:year,month,day,hour,minute
t: start of time offset definition
year: unsigned 16bit integer
range: > 1980
Example: 2026
month: unsigned 16bit integer
range: 1 ~ 12
Example: 2
day: unsigned 16bit integer
range: 1 ~ 31
Example: 10
hour: unsigned 16bit integer
range: 0 ~ 23
Example: 22
minute: unsigned 16bit integer
range: 0 ~ 59
Example: 0Reasons for logger error
- SD card not present
- SD card format not recognized, so unable to mount
- missing config.txt in the root of SD card
- missing head in the root of SD card
- Invalid / Un-recognizable contents in config.txt or head
How to build
Tested features
[!WARNING] Not all aspects of the functionality was tested (This was a side project)
- SDHC card upto 8GB
- Tested baud
- 115200
- 750000
- 921600
- Data bits
- 8
- 9
- Parity
- None
- Stop bits
- 2
- Logging format
c- ASCII charactersu- unsigned decimalx/X- Hexadecimal
- Seq start/Seq stop
\r0xFF0x1CC
Sample log output
Thanks to various open source code base helped realizing the project
- Framework ch32fun
- SD Card driver modified sample driver from ChaN
- FAT(12/16/32) library ChaN's FatFs
- Aleksej Muratov's sscanf modified for this project to further reduce the ROM size
Parts
14| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | 0.1u | Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C2, C4 |
| 2 | Conn_01x02 | swk:1x02_THT_P2.54mm | J3, J4 |
| 1 | 100 | Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R1 |
| 1 | 100uF | Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C1 |
| 1 | 10uF | Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C5 |
| 1 | 1k | Resistor_SMD:R_1206_3216Metric_Pad1.30x1.75mm_HandSolder | R2 |
| 1 | 47uF | Capacitor_SMD:C_1206_3216Metric_Pad1.33x1.80mm_HandSolder | C3 |
| 1 | AZ1117CH-3.3TRG1 | Package_TO_SOT_SMD:SOT-223-3_TabPin2 | U3 |
| 1 | CH32V003F4P6 | swk:TSSOP20 | U1 |
| 1 | Conn_01x03 | swk:1x03_THT_P2.54mm | J2 |
| 1 | Micro_SD_Card | Connector_Card:microSD_HC_Hirose_DM3AT-SF-PEJM5 | J1 |
| 1 | SW_Push_LED | swk:SW_Push_LED_AK104238 | SW2 |
Questions
How big is the Uart data logger PCB?
It measures 25.9 × 19.3 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Uart data logger use?
14 parts, built around the CH32V003F4P6 and AZ1117CH-3.3TRG1. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Uart data logger KiCad files?
From the 123swk123/uart_data_logger repository on GitHub, at the commit this page was made from: the board is schematics/uart_data_logger.kicad_pcb and its schematic schematics/uart_data_logger.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Uart data logger design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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