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.
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.
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.
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