Configuring serial port and baud rate

[Bob Alexander]

Hi,

I'd like to hook my PiDP-11 to my VT52 terminal. I've installed MAX232s and their capacitors, jumpered the serial header (P5) to one of the MAX232's TTL connections (P3) and connected a DB-25 connector to the RS-232 side (P4).

But my head is spinning over what I need to do to configure the PiDP-11 to use the serial port, and how to set the baud rate on it. Any pointers?

Thank you.

[andy]

don't wish to be defeatist :-), but I did the max232/capacitors bit early on but could not get it to work..  in the end I opted for USB/serial converters (good success if using only one or two) and an ethernet terminal server for multiple connections (speeds down to 110)

good luck!

Andy

[ken.r...@gmail.com]

Same for me, would appreciate any pointers. 

my last encounter with PDPs was a custom 11/23 running RT-11

On Tuesday, January 4, 2022 at 1:03:21 PM UTC-5 goo...@LoadAccumulator.com wrote:

[Anton Lavrentiev]

Hi,

If you search this group's messages, all instructions are there... Also Oscar has some in his manual (the .odt file).

Hope this helps,

Anton 

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[Clem Cole]

On the ToDO list is write a HOW-TO for the OpenSIMH site... [truth is this has been discussed and explained in earlier messages and Oscar has some info in his manual].

The short form is the easiest /cheapest way to use modern HW is with USB to RS-232C conversion, although if you can get your hands on something like an old Livingston IP-based Ethernet to 8/16 port MUX of the equiv that works fine.

Linux will recognize most of the USB chips, but .... not all of them have all functionality, and there are trade-offs, for instance, some of the FTCI chips support RTS/CTS-based flow control, but will only go down the 30 cps (300 baud). So I recommend that you find out which chip is being used in the system you are getting and download the datasheet.  FWIW: The ones based on the Prolific PL2303 can support 10 cps (110 baud for a traditional ASR 33), but I've had problems with flow and buffering on some of those cables. There is a third popular chipset (CM340) that is sometimes used.  I have devices with it (Arduinos) and Linux talks to it just fine, but no longer any cables based on it, so I can not give you current experience with SIMH.      I also have a 4 port box that works quite well, I've forgotten the Si that its based on - I think it may be a FTCI 4232 but that's by memory.

Simply plug in the cable -- Linux will recognize it - do a: ls -l  /dev/*usb*   and you should see them.

In simh: type the: show serial command and then "attach DEVXX PATH_reported_by_linux"       <-- DL/KL11, DC11 and DZ11 are popular for most PDP-11 OSses

Now your PiDP-8 or PiDP-11 will have that port as whatever type of device you choose to use.

Also, remember that Linux (which SIMH is running) will accept characters from the emulated OS much faster than the original DEC HW - so people have had issues with different target OS - this causes unexpected/surprising behavior - particularly for newbies. Again all this has been discussed before -- Internet search, and the archives are your friend ;-)

Send me e-mail offline if you need help/explanation.

Clem

ᐧ

[Bob Alexander]

I got it working, but it was a while ago, and I don't remember everything.

In my /home/pi directory, I have a pdp.sh file. Its contents are:

# Serial port is not connected to a UTF-8 device
stty -F /dev/ttyS0 -iutf8

# Second DB-25 is set to 300 baud for DECwriter
stty -F /dev/ttyUSB0 300

procs=`sudo screen -ls pidp11 | egrep '[0-9]+\.pidp11' | wc -l`
echo $procs
if [ $procs -ne 0 ]; then
        sudo screen -d -r

fi

Here's the boot.ini I use for RSTS 10.1 (which is not included in the standard PiDP-11 distribution). Ignore all the disk configuration; just look at the console and tty configurations.

; SIMH command file to run RSTS/E V10.1 on an emulated
; PDP-11/70 cpu with optional floating point,
; 22 bit addressing UNIBUS and 4Mb memory
;
; The pre-installed RSTS/E system has support for
;
; Two RL01/RL02 drives (DL0: and DL1:)
; Two 8-inch floppy drives RX01/RX02 (DX0: and DX1:)
; Four hard disks on RQXD3 controller (DU0: to DU3:)
; Line printer (LP0:)
; Eight terminal lines on DZ11 controller
; Magtape on TS11  (MS0:)
; TK50 tape cartridge (MU0:)

set cpu 11/70
set cpu 4m
set cpu fpp
set cpu idle
set cpu autoconfig
;
; set console switch register for auto restart
d sr 177777
;
; Disable unused/unsupported devices
set rp disable
set cr disable
set hk disable
set rq disable
set rx disable
set tm disable
set vh disable
set ptr disable
set ptp disable
set tc disable
set rk disable

; an RL01 and RL02 disk packs for user data
set rl enable
set rl0 rl01
; David Ahl games
att rl0 rl01-games.dsk
set rl1 rl02
set rl1 locked
;att rl1 rl02-rt11_sys57.dsk
set rl2 disable
set rl3 disable
;
; DY0/DY1 8-inch floppy disks
;
; (usually only works on 18b address system - memory<256KB
; but fine on a PDP-11/70 UNIBUS)
;set ry disable
set ry enable
set ry0 locked
set ry0 single
;att ry0 rx01-floppy.dsk
set ry1 locked
set ry1 double
;att ry1 rx02-blank.dsk
;
;
; MS0: tape drive controller TS11/TSV05
set ts enable
;att ts0 full-backup.tap
show ts0
;
; MU0: (TK50)
set tq enable
set tq tk50
set tq0 locked
set tq0 format=simh
;att tq0 tk50-recovr.tap
;
set tq1 disable
set tq2 disable
set tq3 disable
;
set rq enable
; DU0: system disk RSTS
set rq0 rd53
att rq0 rd53-rsts10_system.dsk
; DU1: user disk USRDSK
set rq1 rd54
;att rq1 rd54-rsts_usrdsk.dsk
; DU2: is a 5.25inch floppy disk
set rq2 rx50
;set rq2 locked
;att rq2 rx50-floppy.dsk

;
set rqb disable
set rqc disable
set rqd disable
;
; Console DL11 uses 8-bit characters
set console serial=/dev/ttyS0;9600-8n1
set tto 8b
set tti 8b
;
; connect to USB serial port
; allow telnet on tcp/ip port 4000 to DZ11 multiplexor
; with 8bit characters

set dz enable
set dz 8b
set dz lines=8
attach dz line=0,connect=/dev/ttyUSB0
attach dz line=1 4000
attach dz line=2 4001
attach dz line=3 4002

;
; ethernet DELUA
;
; Attach Ethernet to a network interface
; Use 'show xu eth' command to show available interfaces.
;
set xu enable
set xub disable
set xu type=delua
set xu mac=08-00-2b-c0-ff-ee
att xu eth0

; connect to panel
set realcons host=localhost
set realcons panel=11/70
; We're running on a desktop PC with connection to localhost: max speed!
set realcons interval=1
set realcons connected
;set realcons debug
;show realcons

;
; boot system disk
;echo Booting RSTS/E V10.1 system disk DU0:
boot rq0

I hope this helps!