2 layers24 × 27.9 mm
2 layers24 × 27.9 mm
Rs485FEC
medo64/Rs485FEC1RS-485 Framework Expansion Card
- Size
- 24 × 27.9 mm
- Copper layers
- 2
- Thickness
- 0.8 mm
- Parts
- 25
- Nets
- 20
- Pads
- 111
- Tracks, vias
- 258, 36
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 21 Aug 2022
- Updated
- 2 Feb 2025
Overview
Rs485FEC is an open-source printed circuit board by medo64, from the medo64/Rs485FEC repository on GitHub, published under the MIT licence. It is a 2-layer board of 24 × 27.9 mm with 25 parts on 20 nets, routed with 258 tracks and 36 vias.
It is built around the SP485EN, FT232RL and AP22652W6, with the B4B-XH-A, CUS08F30 and SM12T1G among its other parts. Its parts include 9 capacitors, 6 resistors, 3 ICs, 2 diodes and 2 connectors. It belongs with the interfaces and adapters boards of this library.
Main components
6
SP485EN
SOP-8-40℃~+105℃ 1 1 2.5Mbps 300uA 32 4.75V~5.25V Half-Duplex Transceiver SOP-8 RS-485 / RS-422 ICs ROHSUMWRS-485 / RS-422 ICs
FT232RL
SSOP-28-208mil-40℃~+85℃ 3.3V~5.25V、4V~5.25V USB 2.0 USB to UART SSOP-28-208mil USB Converters ROHSFTDIUSB Converters
AP22652W6
SOT-26-40℃~+85℃ 1 2.1A 3V~5.5V 65mΩ Active Low High Side Switch Short-Circuit Protection(SCP)、Overcurrent Protection(OCP)、Overtemperature protection (OTP) SOT-26 Power Distribution Switches ROHSDiodes IncorporatedPower Distribution Switches
B4B-XH-A
插件,P=2.5mm,4PUncategorisedJST
CUS08F30
SOD-323Schottky DiodesDOWO
SM12T1G
SOT-23100nA 12V 15A@8/20us 15V 30V 40pF、100pF 450W@8/20us Bidirectional ESD IEC 61000-4-2、IEC 61000-4-5、IEC 61000-4-4 SOT-23 ESD and Surge Protection (TVS/ESD) ROHSTECH PUBLICESD And Surge Protection (TVS/ESD)
README
README.mdRS-485 Framework Expansion Card
This Framework laptop expansion card will show up on your system as a serial device and allow for non-isolated RS-485 communication up to 3,000,800 baud rate.
Please note that this card is using automatic transmit control and is 120Ω terminated.
Pinout
To connect to this board, one has to use a 4-pin JST XH connector. The following table represents the pinout, pin 1 being on the left as looking into the expansion card.
| # | Ref | Description |
|---|---|---|
| 1 | GND | Ground connection |
| 2 | A | Negative (low for logic 1 and high for logic 0) |
| 3 | B | Positive (high for logic 1 and low for logic 0) |
| 4 | 5V | 100 mA power supply |
As power consumption is low, wires can be almost any AWG. I would recommend using 24 AWG wire 0.25 mm² as they allow for greater compatibility with other connectors.
Supported Speeds
This board employs the FT232R as its UART chip, and consequently, it supports all the baud rates this chip can handle up to 500,000 baud which is the limit of isolator chip used. The table below lists the standard baud rates.
| Baud rate | Actual | Error | Divisor |
|---|---|---|---|
| 300 | 300 | 0.00% | 10000.000 |
| 600 | 600 | 0.00% | 5000.000 |
| 1,200 | 1,200 | 0.00% | 2500.000 |
| 1,800 | 1,800 | 0.00% | 1666.625 |
| 2,400 | 2,400 | 0.00% | 1250.000 |
| 4,800 | 4,800 | 0.00% | 625.000 |
| 7,200 | 7,201 | 0.01% | 416.625 |
| 9,600 | 9,600 | 0.00% | 312.500 |
| 14,400 | 14,406 | 0.04% | 208.250 |
| 19,200 | 19,200 | 0.00% | 156.250 |
| 28,800 | 28,812 | 0.04% | 104.125 |
| 38,400 | 38,400 | 0.00% | 78.125 |
| 57,600 | 57,692 | 0.16% | 52.000 |
| 115,200 | 115,385 | 0.16% | 26.000 |
| 230,400 | 230,769 | 0.16% | 13.000 |
| 460,800 | 461,538 | 0.16% | 6.500 |
| 921,600 | 923,077 | 0.16% | 3.250 |
| 1,000,000 | 1,000,000 | 0.00% | 3.000 |
| 2,000,000 | 2,000,000 | 0.00% | 2.000 |
| 3,000,000 | 3,000,000 | 0.00% | 0.000 |
While rates above this can be set, they are not guaranteed to work.
You can check my blog and other projects at www.medo64.com.
Parts
25| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | 100n | Medo64:C (0805) | C2, C3, C4, C5, C6 |
| 3 | 10u | Medo64:C (0805) | C7, C8, C9 |
| 2 | 1K | Medo64:R (0805) | R2, R3 |
| 1 | 105444-0001 | Medo64:J USB C 3.2 Edge (24w) | J1 |
| 1 | 10K | Medo64:R (0805) | R5 |
| 1 | 10n | Medo64:C (0805) | C1 |
| 1 | 120 | Medo64:R (0805) | R1 |
| 1 | 5K1 | Medo64:R (0805) | R5 |
| 1 | 600R | Medo64:L (0805) | L1 |
| 1 | 75K | Medo64:R (0805) | R6 |
| 1 | AP22652 | Medo64:U LoadSwitch Adjustable [AP22652W6-7] (SOT23-6) | U3 |
| 1 | B4B-XH-A | Medo64:J JST XH Edge [RS485] (4w) | J2 |
| 1 | CUS08F30 | Medo64:D (SOD323) | D1 |
| 1 | FT232RL | Medo64:U Transceiver UART [FT232R] (SSOP-28) | U1 |
| 1 | RX | Medo64:DS (0805) | DS1 |
| 1 | SM12T1G | Medo64:D TVS 7-12V [SM712] (SOT23-3) | D2 |
| 1 | SP485E | Medo64:U Transciever RS485 [SP485EEN] (SOIC-8) | U2 |
| 1 | TX | Medo64:DS (0805) | DS2 |
Questions
How big is the Rs485FEC PCB?
It measures 24 × 27.9 mm and has 2 copper layers, 0.8 mm thick.
What parts does the Rs485FEC use?
25 parts, built around the SP485EN, FT232RL, AP22652W6 and B4B-XH-A. 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 Rs485FEC KiCad files?
From the medo64/Rs485FEC repository on GitHub, at the commit this page was made from: the board is src/Rs485FEC.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Rs485FEC 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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