How do I configure parameters for 3 wire serial?

[ModMike]

I am trying to connect to a 3D printer board using 3 wire serial, that is no CTS and RTS. I had a Wemos wifi module on it previously so I know it works. Now I need to use my BanaPi M2 Zero to control it thorough the same port, the Wemos has been removed and not going back. I keep getting a failure to initialize when I try to connect to the board. 

 

I am trying to use Pins 8 & 10 which is supposed to be UART 3 = /dev/ttyS3 from what I understand.

 

Questions:

 

1. How can I test the port? I have Minicom installed.
2. How do I set the parameters to disable CTS and RTS?
3. What flow control should I be using? Software?

 

 

Here is my setup:

 

armbianEnv.txt 

 

verbosity=1
bootlogo=false
console=both
disp_mode=1920x1080p60
overlay_prefix=sun8i-h3
rootdev=UUID=e7e80086-a15f-4f2e-825d-9913c71ff19c
rootfstype=ext4
usbhost0
overlays=uart3 usbhost0
param_uart3_rtscts (bool)
    Enable RTS and CTS pins
    Optional
    Default: 0
    Set to 1 to enable CTS and RTS pins
usbstoragequirks=0x2537:0x1066:u,0x2537:0x1068:u

 

Is that the correct parameters fro disabling RTS and CTS for 3 wire serial? I am using RX and TX cross connected as well as ground. Both boards are independently powered.

 

Other data:

 

My serial port seems to be working, see bold line:

 

dmesg | grep tty

[    0.000000] Kernel command line: root=UUID=e7e80086-a15f-4f2e-825d-9913c71ff19c rootwait rootfstype=ext4 console=ttyS0,115200 console=tty1 hdmi.audio=EDID:0 disp.screen0_output_mode=1920x1080p60 consoleblank=0 loglevel=1 ubootpart=bfca11dd-01 ubootsource=mmc usb-storage.quirks=0x2537:0x1066:u,0x2537:0x1068:u   sunxi_ve_mem_reserve=0 sunxi_g2d_mem_reserve=0 sunxi_fb_mem_reserve=16 cgroup_enable=memory swapaccount=1

[    0.000352] printk: console [tty1] enabled

[    2.223565] printk: console [ttyS0] disabled

[    2.223659] 1c28000.serial: ttyS0 at MMIO 0x1c28000 (irq = 44, base_baud = 1500000) is a 16550A

[    2.223915] printk: console [ttyS0] enabled

[    2.225223] 1c28400.serial: ttyS1 at MMIO 0x1c28400 (irq = 45, base_baud = 1500000) is a 16550A

[    2.225410] serial serial0: tty port ttyS1 registered

[    2.226212] 1c28c00.serial: ttyS3 at MMIO 0x1c28c00 (irq = 46, base_baud = 1500000) is a 16550A

[    6.072173] systemd[1]: Created slice system-serial\x2dgetty.slice.

[    7.101175] systemd[1]: Found device /dev/ttyGS0.

[    8.576630] systemd[1]: Found device /dev/ttyS0.

 

Second Test:

 

sudo setserial -g /dev/ttyS3

/dev/ttyS3, UART: 16550A, Port: 0x0000, IRQ: 46

 

[tparys]

Couple of thoughts:

 

1 - You probably mean RS232 serial, and not 485. Both are 3 wire serial. Just FYI.

 

2 - The setserial application is exclusively for ISA bus based serial ports. I doubt you have one of these. You can look at stty if you want, but generally whatever software you run will set those parameters for you at run-time. There's no system-level configuration you'll need to do aside from making the port active. If it's showing up in the kernel log, that's a good start.

 

3 - The big parameters you'll want to worry about are baud rate, and disabling HW flow control. There's a bunch of other settings too which are more rare, such as number of data bits, parity, and stop bits. Unless you have documentation that says otherwise, assume 8 data bits, no parity, 1 stop bit (sometimes listed as 8N1).

 

4 - If you want to test with minicom, be aware it enables HW flow control by default. You can change this default by doing:

 

$ sudo minicom -s
<Select "Serial Port Setup">
<Hit 'F' to set "Hardware Flow Control" to "OFF">
<Hit Esc>
<Select "Save setup as dfl">

 

You may also want to add your user to the "dialout" group. You'll probably want to log out/back in afterwards.

 

$ sudo usermod -aG dialout <username>

 

 Then you can launch minicom on that port by doing this:

 

$ minicom -D /dev/ttyS3 -b <printer baud here>

 

 

[ModMike]

Thank you for the tips. I think baud rate was my biggest issue and yes I meant RS-232.

 

Are my parameters properly configured? How can I turn off RTS and CTS? I am unsure of the parameter syntax.

 

Thanks again!

 

 

[tparys]

Depends on what program you're accessing the serial port.

 

For minicom, you disable the "Hardware Flow Control" as above via "minicom -s".

 

If you're using stty, it's the crtscts flag (see "man stty").

 

For C programming, it's the CTSRTS flag (see "man tcsetattr").

 

Past that, I don't know what software you're trying to drive your printer, so can't tell you what parameters you need.

[ModMike]

I am not using uart to connect to the computer. I am using it to the 3d printer control board, it's a Fysetc Cheetah. I have it working with a regular pi and raspbian. On PI, all I had to do was disable serial console and enable uart.

 

Trying to do the same on Armbian so I can use a BPI instead of a zero. Can you please tell me how to use the parameters to disable RTS and CTS and which port name is assigned to GPIO 14 & 15 (physical pins 8 & 10).

 

Thanks!

[tparys]

As far as I'm aware, there is no OS level control to disable RTS/CTS pins. It's entirely in the user application accessing the UART/Serial Port, per my last post.

 

Not familiar with the BPi at all, so you'll have to find that in the documentation.

 

Past this, I cannot help you. Good luck.