On Sat, Feb 18, 2017 at 11:35:51AM +0100, Maarten Brock wrote: > On 2017-01-30 12:12, Fabio Estevam wrote: > > From: Fabio Estevam <fabio.estevam@xxxxxxx> > > > > When userspace passes the SER_RS485_RTS_ON_SEND flag it means that the > > CTS_B pin should go to logic level high before the transmission begins. > > So setting the SER_RS485_RTS_ON_SEND flag sets CTS_B active high during > send. No, CTS_B is an active-low output, so SER_RS485_RTS_ON_SEND leads to a logic level low CTS_B during transmit. > > > When userspace passes the SER_RS485_RTS_AFTER_SEND flag it means that > > the > > CTS_B pin should go to logic level low after the transmission finishes. > > And setting the SER_RS485_RTS_AFTER_SEND flag sets CTS_B active low after > send ? No, this also sets CTS_B to logic level low, but after the transmission ends. > > I don't get it. First, isn't CTS an input instead of an output? On the i.MX6, CTS_B is an output and can be connected for example to the transceive-enable input of a RS-485 transceiver. The name is confusing, I guess this is due to the different meaning in DTE/DCE mode. > And if I follow this through and want CTS_B high during a transmit only then > I > must set both SER_RS485_RTS_ON_SEND and SER_RS485_RTS_AFTER_SEND. If you want CTS_B to be logic high during transmit, then you only set SER_RS485_RTS_AFTER_SEND and clear SER_RS485_RTS_ON_SEND. On our board we invert the signal in hardware, so we can use the default setting (only SER_RS485_RTS_ON_SEND), then go through the inverter to the active-high transmit-enable input of the transceiver. Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
