Guide to using the external serial - Jeff Tranter's blog

Discuss the new Altair 8800 Micro

Guide to using the external serial - Jeff Tranter's blog

Postby waltermixxx » Apr Sun 26, 2015 3:53 pm

i tried starting the 8800 micro without the keyboard, which dissables the pocket terminal portion of the 8800micro, so i thought would enable the serial port connected to the expansion port...

i know there is no hand shaking but what do we set the baud rate to?

I'm using putty, have the serial port set to 8N1 no handshaking and no parity.
i use cntrl shift F7 and cntrl alt F7 to adjust serial port settings on the 8800micro.
and i only get gobbledy gook on the putty screen...

I tried 9600 baud for both text and binary

there is only the 1 serial port on this computer correct? connected between the prop and the 8515 chips...
i'm guessing the expansion port serial card simply connects to those two signals... and there should be able to "monitor" communication between the prop and the 8515?

i used a serial laplink like cable with both female to female 9 pin and 25pin connectors on each end. ( I use it when connecting my Amiga 500 to my pc for amiga explorer) so i know the cable is good :)

how about a for dummies guide on this ? :)
Last edited by waltermixxx on Apr Mon 27, 2015 9:01 am, edited 1 time in total.
waltermixxx
 
Posts: 86
Joined: Mar Mon 30, 2015 1:02 pm
Location: Toronto, Ontario

Re: Is there a guide to using the external serial port?

Postby waltermixxx » Apr Sun 26, 2015 5:12 pm

Ok i had a brief read through this document on wireless serial connection:

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB0QFjAA&url=https%3A%2F%2Fdocs.google.com%2Fdocument%2Fd%2F1c1TBfCwY4sS6dAQfkF-kgntKxOcZEtHUsKt6GNLX46o%2Fedit%3Fusp%3Dsharing&ei=rE89Vdz_MovMsAXDjYGgAg&usg=AFQjCNGqqDQeXnLICMILPeHIHi7SzxWvGQ&sig2=IjLuZBEYjUS98qwMVre5Kg

The external serial port is connected to the TXD RXD lines on the expansion port, which is also connected to the 8515.

I can dissable the built in terminal with Crtl - F7 I'm still not seeing anything on my computer via the serial port.
what should i set my serial port on my computer to? the baud rate has to match, that i know, so if the 8800 is 9600 so should be the serial port.


i tried 2 computers... my laptop through a usb to serial connector and my desktop with a serial port...

:( I know i must be doing sometihng wrong... Any help appreciated :)
waltermixxx
 
Posts: 86
Joined: Mar Mon 30, 2015 1:02 pm
Location: Toronto, Ontario

Re: Is there a guide to using the external serial port?

Postby waltermixxx » Apr Sun 26, 2015 7:51 pm

I found this very informative blog with information on the serial port, and based on what I have read, I'm thinking there may be an issue with my serial card... I double checked the soldering and it looks totally fine, no blobs, nothing sick, just nice shiny solder joints...

Thank you Jeff Tranter's blog!! :)

http://jefftranter.blogspot.ca/2014/03/ ... erial.html

I've worked with serial ports before, modems all the old school stuff. use it often on my vintage computers...
i will have to try it with a ftdi and connect directly to the rxd and txd pins... either with a 3.3 volt ftdi, or with 1k resisters. :)

Thanks Jeff :)
waltermixxx
 
Posts: 86
Joined: Mar Mon 30, 2015 1:02 pm
Location: Toronto, Ontario

Re: Is there a guide to using the external serial port?

Postby waltermixxx » Apr Sun 26, 2015 11:23 pm

I had some success with the ftdi and connecting directly to pin 21 and 22 and grn, i could see there was plenty of action on the serial pins,
but nothing on the serial port expansion board... I am starting to think none of my "nul modem cables" are actually nul modem cables...
so i am pretty sure i have one at work still in the package and labeled null modem cable...

:) i hope that is the problem...

using the ftdi, was wierd, the Altair would freeze up and it was difficult to get consistant behavior with it...
i had to change to 7M1 and could read the text on the pc, but could not type on the pc and get the data on the altair...
I am really hoping a new null modem cable simplified the process. :0
waltermixxx
 
Posts: 86
Joined: Mar Mon 30, 2015 1:02 pm
Location: Toronto, Ontario

Re: Guide to using the external serial - Jeff Tranter's blog

Postby waltermixxx » Apr Wed 29, 2015 12:08 am

Happy to say I got my Serial port working... the header cable wiring was going 1357 on the top row and 2468 on the bottom row or something along those lines... So I rewired the connections for just ground to pin 5 and transmit and recieve to 2 & 3, and it's working now as described in Jeff's blog. I did notice the strangeness when starting up the 8800micro, with the serial cable plugged in, and the INP light flashing... I found that if i reset or restarted the 8800micro with the cable hooked up, but did not launch your terminal program until after the Altair booted (so to speak) it worked fine with no issues... so connect everything up, start up your 8800, then launch your term program :)

Image

I do have a question, does anyone have the schematic for the serial port board? are any other connections made to the male serial port?
as you can see i reduced it to 3 signals, Groud, Send and Receive... so if there are any other signals going from the chip to the header,
or perhaps other pins of the header connected together? or should i not worry about it and just stick to ground send and receive?

please advise... in the mean time, happy my terminal is working ( I really was going nuts trying to figure out why non of my cables were working... )

Now I love my Altair even Moore... ( so to spreak...) :)
waltermixxx
 
Posts: 86
Joined: Mar Mon 30, 2015 1:02 pm
Location: Toronto, Ontario

Re: Guide to using the external serial - Jeff Tranter's blog

Postby Kryoclasm » Jun Sun 28, 2015 12:02 am

This is good info. I will me messing with this soon too. :)
Kryoclasm
 
Posts: 21
Joined: May Fri 22, 2015 5:22 pm

Re: Guide to using the external serial - Jeff Tranter's blog

Postby wmaalouli » Jan Sun 19, 2020 10:04 pm

waltermixxx wrote:Happy to say I got my Serial port working... the header cable wiring was going 1357 on the top row and 2468 on the bottom row or something along those lines... So I rewired the connections for just ground to pin 5 and transmit and recieve to 2 & 3, and it's working now as described in Jeff's blog. I did notice the strangeness when starting up the 8800micro, with the serial cable plugged in, and the INP light flashing... I found that if i reset or restarted the 8800micro with the cable hooked up, but did not launch your terminal program until after the Altair booted (so to speak) it worked fine with no issues... so connect everything up, start up your 8800, then launch your term program :)

Image

I do have a question, does anyone have the schematic for the serial port board? are any other connections made to the male serial port?
as you can see i reduced it to 3 signals, Groud, Send and Receive... so if there are any other signals going from the chip to the header,
or perhaps other pins of the header connected together? or should i not worry about it and just stick to ground send and receive?

please advise... in the mean time, happy my terminal is working ( I really was going nuts trying to figure out why non of my cables were working... )

Now I love my Altair even Moore... ( so to spreak...) :)

I know this is few years late but I have finally managed to find the time to build the kit along with the serial adapter and RAM disk...

I'm not too clear how this wiring setup is working for you. According to the picture, the TX pin on the serial adapter is connected to ground on the db9 cable, and the adapter ground is going to the Ring indicator on the db9???
To answer your question, only the TX, RX and ground pins are connected to the DB9 connector. You can swap the RX and TX if you don't want to use a null modem cable.
The external serial functionality on this kit is a little dodgy. In my case, the only way I am able to get external serial I/O is by having the computer autoload a program like 8k basic with the ps2 keyboard disconnected. Go figure...
Incidentally, to setup a file for autoload, flip the AUX and pin 12 up then power the computer. At the prompt type in the filename then press SHIFT ENTER. At the next boot with the same switch setup, the program will load automatically. Works great gor basic.
wmaalouli
 
Posts: 1
Joined: Mar Fri 20, 2015 12:06 am


Return to Altair 8800 Micro

Who is online

Users browsing this forum: No registered users and 6 guests

cron