Except that we've just made all that stuff irrelevant, so enabling it has no effect. That's really saying "enable all the RS485-specific stuff that's controlled by this structure". The fact that some of those messages may have originated from you doesn't matter.įinally (and firstly) we have this /* Enable RS485 mode: */ RS485 is multidrop, so you should be filtering out messages that were not addressed to you anyway. Since this device has a dedicated TXDEN pin, those control fields are irrelevant.Īnother flag that is used in this structure: /* Set this flag if you want to receive data even whilst sending data */Īnd yes looking at the circuit, what you put out on the line you will also receive. If we pick apart struct serial_rs485 we can see that it is mostly about controlling RTS for this purpose. Provided for exactly that purpose, and so the transmitter enables are wired to the TXDENĪnd you can see that the RS232 outputs RTS / DTR not connected in RS485, this is in contrast to devices where RTS becomes TXDEN which would require an intervention by the driver. Is only enabled when a character is being transmitted from the UART. Quoting from the Data sheet section 4.3.3 However this device has a dedicated pin called TXDEN for that. Half-duplex hardware like an RS485 transceiver. Half-duplex mode capable of automatically controlling line direction by
Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in Quoting from the Kernel document you referenced
However, as discussed that didn't solve the problem. Rs485conf.flags |= SER_RS485_RX_DURING_TX
* Set this flag if you want to receive data even whilst sending data */ * Set rts delay after send, if needed: */ * Set rts delay before send, if needed: */ * set logical level for RTS pin equal to 0 after sending: */ Rs485conf.flags |= SER_RS485_RTS_ON_SEND * Set logical level for RTS pin equal to 1 when sending: */ I am using the following code to access the RS485 slave but I get the error:Įrror reading ioctl port (25): Inappropriate ioctl for device
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