An RS-485 port (J5) is provided on UART1 for the testing of custom drivers to be written by a developer. Table 4 provides RS-485 connector pinouts.
Table 4. RS-485 port pinouts
Pin | Signal |
---|---|
1 | RS-485 Signal B (-) |
2 | RS-485 Signal A (+) |
3 | Reference Ground (S) |
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To drive the RS-485 interface, UART1 must be used in 2-wire mode, and DIO17 and DIO18 are used to control the enable signals on the RS-485 device. Table 5 shows the functions provided:
Table 5. DIO18 (DE) and DIO17 (REN) functions for RS-485 interface
DIO18 (DE) | DIO17 (REN) | Function |
---|---|---|
0 | 0 | Rx Mode |
0 | 1 | Shutdown. Use this mode to save current when the module sleeps. |
1 | 0 | Do not use. |
1 | 1 | Tx Mode |
If the RS-485 interface is not required, then all four signals can be disconnected from the RS-485 by removing resistors R28, R29, R32 and R34. This allows the signals to be used on expansion header J4.
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