--
Henri Roosen | Entwicklung Software
GINZINGER ELECTRONIC SYSTEMS GMBH
Tel.: +43 7723 5422 161
Mail: Henri.Roosen@xxxxxxxxxxxxx
Web: www.ginzinger.com
On Fri, 2022-08-05 at 10:18 +0200, Lukas Wunner wrote:
> On Thu, Aug 04, 2022 at 04:11:26PM +0000, Roosen Henri wrote:
> > On Thu, 2022-08-04 at 17:52 +0200, Lukas Wunner wrote:
> > > On Thu, Aug 04, 2022 at 02:38:23PM +0000, Roosen Henri wrote:
> > > > unfortunately this commit, which has been backported to v5.4.x,
> > > > seems
> > > > to break RS485 functionality on our iMX boards.
> > >
> > > What exactly broke? Are you seeing incorrect polarity after
> > > opening
> > > the tty but correct polarity after the first send? Or is polarity
> > > always incorrect?
> >
> > I'm not sure about the state before opening, I have to measure that
> > when I'm back at the office.
> >
> > After opening, the polarity is always incorrect (inverted) when
> > this
> > patch is applied. We open the tty and try to receive, which now
> > fails
> > because the rs485 transmitter is on.
>
> Does reception work after you send something?
No, it does not. This is because RTS is high during reception.
I'll provide you some oscilloscope screenshots off-list, but in words,
with this patch:
- the RTS is low at boot
- there is a small glitch (high-low pulse) when configuring the speed
using 'stty -F /dev/ttymxc2 230400 raw -echo'
- RTS goes high when receiving, using 'cat /dev/ttymxc2'
- after stopping the cat command, RTS stays high
- RTS goes low for a few microseconds then high, just before
transmitting the first data using 'echo hello > /dev/ttymxc2'
- RTS stays high while sending data
- RTS goes low after sending data, and stays low
Without this patch, RTS is only high during data transmission.
>
> Please provide the contents of the pinctrl_uart2_rs485 node in your
> DT.
#define UART_PAD_CTRL ( \
PAD_CTL_ENABLED | \
PAD_CTL_SION_OFF | \
PAD_CTL_HYS_ON | \
PAD_CTL_PUS_100K_UP | \
PAD_CTL_PUE_ON | \
PAD_CTL_PKE_ON | \
PAD_CTL_ODE_OFF | \
PAD_CTL_SPEED_MED | \
PAD_CTL_DSE_40ohm | \
PAD_CTL_SRE_FAST)
pinctrl_uart2_rs485: uart2rs485grp {
fsl,pins = <
MX6UL_PAD_UART2_RX_DATA__UART2_DCE_RX UART_PAD_CTRL
MX6UL_PAD_UART2_TX_DATA__UART2_DCE_TX UART_PAD_CTRL
MX6UL_PAD_UART2_RTS_B__GPIO1_IO23 UART_PAD_CTRL
>;
};
>
> Thanks,
>
> Lukas
Ginzinger electronic systems GmbH
Gewerbepark 3
4950 Altheim
www.ginzinger.com <https://www.ginzinger.com/>
Firmenbuchnummer: FN 364958d
Firmenbuchgericht: Ried im Innkreis
UID-Nr.: ATU66521089
Diese Nachricht ist vertraulich und darf nicht an andere Personen weitergegeben oder von diesen verwendet werden. Verständigen Sie uns, wenn Sie irrtümlich eine Mitteilung empfangen haben.
This message is confidential. It may not be disclosed to, or used by, anyone other than the addressee. If you receive this message by mistake, please advise the sender.
Attachment:
smime.p7s
Description: S/MIME cryptographic signature
