3.3V UART Framework Expansion Card
This Framework laptop expansion card will show up on your system as a serial device and allow for a non-isolated serial UART communication up to 1 Mbaud.
Please note that this card is not using RS-232 but 3.3V TTL.
UART 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 |
|---|---|---|
| 2 | GND | Ground connection |
| 1 | RXD | Receive (3.3V TTL) |
| 3 | TXD | Transmit (3.3V TTL) |
| 4 | 3V3 | 3.3V 400mA (typical) output |
Using 22 AWG wire 0.25 mm² is recommended.
Supported Speeds
This board employs the FT232R as its UART chip, and consequently, it supports all the baud rates this chip can handle. 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 |
While chip does support baud rates up to 3 Mbaud, granularity of such rates is severely limited.