Date   
Re: I2C Interface For Membership Card

bill rowe
 

I'm not sure what we're looking at in the trace but the signals look quite glitchy - i assume it doesn't matter?  Let's see it DO something though!

The Olduino has hardware SPI but i have never done anything with I2C.


From: cosmacelf@groups.io <cosmacelf@groups.io> on behalf of Rick <rppolicy@...>
Sent: February 22, 2020 4:33 PM
To: cosmacelf@groups.io <cosmacelf@groups.io>
Subject: [cosmacelf] I2C Interface For Membership Card
 

[Edited Message Follows]

I'd like to start off by apologizing to anyone who would prefer to keep the Membership card in the spirit of its time.

However, I thought it would be a huge advantage to add an I2C bus master interface (sacrilege!).  That way, it opens the door for more graphics options such as OLED displays since Pixie is getting harder to find (at least for me).

The root of my design is the PCF8584 from NXP.  It seems to interface nicely to the CDP1802 with a little bit of glue logic since it has an 80xx compatibility mode.  

I've attached the schematic.  The schematic includes decoding for the CDP1854 UART, the I2C bus master, and two extra chip selects (CS1 and CS7).  I put a HCT254 in front of the PCF8584 since it is not exactly CMOS compatible.  The PCF8584 VIH will be fine, but according to the datasheet the VOH is rated as: VOH is 2.4 V when sourcing 2.4mA.  It doesn't have the traditional VOH specification.  That being said...  I believe the HCT245 is not needed since it is interfacing to CMOS.  I confirmed that the device drives the bus solidly at 5V when logic 1.  I decided to keep the HCT245 since I may be adding more devices.

I tested the circuit using an Adafruit 16 channel PWM board.  See the attached scope captures.

PS: I already had assembly code for the PCF8584 and PWM board for MC6800 and MC6809 retro computers that I built.  My mistake was translating the assembly code to BASIC3 since I thought it would be faster.  Boy did I find out in a hurry that my BASIC skills died in high school (a bazillion years ago)!!!  It took me much longer than it should...

- Rick

--
Bill Rowe
Olduino - an arduino for the first of us
https://olduino.wordpress.com/about-2/about/

Re: I2C Interface For Membership Card

bill rowe
 

such wires!


From: cosmacelf@groups.io <cosmacelf@groups.io> on behalf of Rick <rppolicy@...>
Sent: February 22, 2020 4:39 PM
To: cosmacelf@groups.io <cosmacelf@groups.io>
Subject: Re: [cosmacelf] I2C Interface For Membership Card
 
Oh, here's a pic of my prototype...

- Rick

--
Bill Rowe
Olduino - an arduino for the first of us
https://olduino.wordpress.com/about-2/about/

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Re: Free RCA 1861 Pixie Chip date code 814

Ham Radio
 

The pixie chip has been spoken for.   

If the current deal deal does not happen,  Greg, you were second to reply.
--
Regards,
Bernie Murphy

Re: Free RCA 1861 Pixie Chip date code 814

gregory simmons
 

Bernie, I could give this pixie a good home.  

Free RCA 1861 Pixie Chip date code 814

Ham Radio
 

Yes, it is true.

I have no way of testing this chip.  There are two broken pins - the solution would be to mount in a 24 pin socket and solder in the two broken pins to the socket.

The carrier is ceramic colour purple.

You pay postage which should be about $10.00 or so depending on your location.


--
Regards,
Bernie Murphy

Re: I2C Interface For Membership Card

Rick
 

Oh, here's a pic of my prototype...

- Rick

I2C Interface For Membership Card

Rick
 
Edited

I'd like to start off by apologizing to anyone who would prefer to keep the Membership card in the spirit of its time.

However, I thought it would be a huge advantage to add an I2C bus master interface (sacrilege!).  That way, it opens the door for more graphics options such as OLED displays since Pixie is getting harder to find (at least for me).

The root of my design is the PCF8584 from NXP.  It seems to interface nicely to the CDP1802 with a little bit of glue logic since it has an 80xx compatibility mode.  

I've attached the schematic.  The schematic includes decoding for the CDP1854 UART, the I2C bus master, and two extra chip selects (CS1 and CS7).  I put a HCT254 in front of the PCF8584 since it is not exactly CMOS compatible.  The PCF8584 VIH will be fine, but according to the datasheet the VOH is rated as: VOH is 2.4 V when sourcing 2.4mA.  It doesn't have the traditional VOH specification.  That being said...  I believe the HCT245 is not needed since it is interfacing to CMOS.  I confirmed that the device drives the bus solidly at 5V when logic 1.  I decided to keep the HCT245 since I may be adding more devices.

I tested the circuit using an Adafruit 16 channel PWM board.  See the attached scope captures.

PS: I already had assembly code for the PCF8584 and PWM board for MC6800 and MC6809 retro computers that I built.  My mistake was translating the assembly code to BASIC3 since I thought it would be faster.  Boy did I find out in a hurry that my BASIC skills died in high school (a bazillion years ago)!!!  It took me much longer than it should...

- Rick

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Re: Todd's ELF-ish to get an FDC #Homebrew #microboards

cellarcat
 

Hi, Todd! I added a 50 pin connector to my board because I run Microdos with 8” drives. The original 3.5 inch drives rotated at 600 rpm which gave the same data rate as an 8” drive. I have an original Sony 600 rpm 3.5” drive but I could never get it to run properly. I suspect it needs a major recalibration. Which led me to the Gotek floppy emulators. If you flash them with the HxC firmware you can recreate almost any drive ever made. I set mine up for 600 rpm, 500000 bit rate and loaded Dave’s Microdos image file. It worked perfectly. I then attached an 8 inch drive as Drive 1 and used Format and Sysgen to transfer the operating system to an 8 inch disk. 

Thanks for letting me know the changes you have made to the schematics. My board is designed to plug into the 44 pin RCA bus and I was surprised at how short most of the connections are. It never hurts to buffer though.

I’m not sure the Gotek drives actually have a model number. Mine just say Gotek. They are really cheap on Ebay and are usually designated for use with various musical instruments. The secret is to give them the HxC firmware which can be purchased here:
When used with the HxC floppy emulator software almost any drive ever made, if not every drive ever made, can be reproduced. I have used them with several CP/M machines and they can be lifesavers.



On Feb 21, 2020, at 5:12 PM, taf123 <todd.ferguson@...> wrote:

Hi again Cellarcat!

Bummer about the 18S651 - I was happy to hear that you had gotten that going.  Be interested if you can track it down.  By the way, what's the model numbers of those floppy emulators you have in that pic?

Nice spot on the schematic. I did the exact same thing with INDCL on pin 4 of U14A to pin 5 of U7B.  Funnily enough, my pattern matching didn't even notice while building and I wired it correctly ;-)

Fixed.

I made some changes/corrections compared to the schematic the is currently available. 
  • I buffered SC0 and SC1.  This required changing U4 to an 74HC244.  Across the complete ELF-ish, those lines travel quite a ways without any buffering.  Your mileage may vary.
  • Added pull-up resistors to U24 MOTON0-4 lines
  • The !CLR pins (P2) on U21 and U22 should be driven by !CLEAR instead of CLEAR - oops.
    • Decided to buffer !CLEAR as well
  • Added a jumper block to set all four drive motors always on.
  • Changed the drive of LCT from U12D to U16B so it wouldn't have to be such a long wire run there and back.
  • In the picture, you can see I have an additional power distribution point in the upper half of the board, just under the 34-pin connectors, and I decided to add a 10uF tan there.  This is C2 on page 1.

There could be other minor changes.

Not knowing anyone was following along, I hadn't uploaded the changed.  Now I have, as ELF-BB-FDC-II_20200221.pdf.

Best regards,
Todd

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Re: Todd's ELF-ish to get an FDC #Homebrew #microboards

taf123
 

Hi again Cellarcat!

Bummer about the 18S651 - I was happy to hear that you had gotten that going.  Be interested if you can track it down.  By the way, what's the model numbers of those floppy emulators you have in that pic?

Nice spot on the schematic. I did the exact same thing with INDCL on pin 4 of U14A to pin 5 of U7B.  Funnily enough, my pattern matching didn't even notice while building and I wired it correctly ;-)

Fixed.

I made some changes/corrections compared to the schematic the is currently available. 
  • I buffered SC0 and SC1.  This required changing U4 to an 74HC244.  Across the complete ELF-ish, those lines travel quite a ways without any buffering.  Your mileage may vary.
  • Added pull-up resistors to U24 MOTON0-4 lines
  • The !CLR pins (P2) on U21 and U22 should be driven by !CLEAR instead of CLEAR - oops.
    • Decided to buffer !CLEAR as well
  • Added a jumper block to set all four drive motors always on.
  • Changed the drive of LCT from U12D to U16B so it wouldn't have to be such a long wire run there and back.
  • In the picture, you can see I have an additional power distribution point in the upper half of the board, just under the 34-pin connectors, and I decided to add a 10uF tan there.  This is C2 on page 1.

There could be other minor changes.

Not knowing anyone was following along, I hadn't uploaded the changed.  Now I have, as ELF-BB-FDC-II_20200221.pdf.

Best regards,
Todd

Re: Todd's ELF-ish to get an FDC #Homebrew #microboards

cellarcat
 

Go for it!! This is your baby and your work. I am just a slavish copier. I have no doubt there are multiple errors in my wire wrapping that will take me some time to sort out. The reason I built your board is because of some peculiar problems I am having with my 18S651. For some unknown reason it suddenly started refusing to load files that had more than 8 contiguous sectors. On the 8th sector I get a term error after 5 unsuccessful tries to read the sector. And this happens even if the sectors cross a track boundary. Less than 8 sectors and the file loads fine. Nuts!!

By the way in your schematic pin 5 of U14A is shown as OUTDCI but the input pin 4 to U9B is OUTDCI with a negative bar over it. I couldn’t find another OUTDCI anywhere so I am assuming this is just a typo. Otherwise I did not find any errors in your schematic which is certainly a credit to your meticulous work. I have found multiple errors in RCA’s schematics!

I look forward to hearing that you have the Elfish purring away and if you have any problems with Microdos loading please contact me because I went through a lot of trial and error getting it to work with the 651.




On Feb 21, 2020, at 3:15 AM, taf123 <todd.ferguson@...> wrote:

Hi cellarcat -

I think it's fantastic that you are building my variant on this board - very cool!

But can I ask one favor - given the time and effort that I've put into it, please don't steal my thunder now that I'm in the home stretch.

I still have to whip up a memory board to support the 2K ROM and rest filled with RAM, plus do some updates to the other expansion chassis.

That's what's on the schedule for this weekend. I guess I'll be keeping the coffee flowing ;-)

Cheers,
Todd

Re: Todd's ELF-ish to get an FDC #Homebrew #microboards

taf123
 

Hi cellarcat -

I think it's fantastic that you are building my variant on this board - very cool!

But can I ask one favor - given the time and effort that I've put into it, please don't steal my thunder now that I'm in the home stretch.

I still have to whip up a memory board to support the 2K ROM and rest filled with RAM, plus do some updates to the other expansion chassis.

That's what's on the schedule for this weekend. I guess I'll be keeping the coffee flowing ;-)

Cheers,
Todd

Re: Todd's ELF-ish to get an FDC #Homebrew #microboards

cellarcat
 

And the race is on! I have been building your board as well and am almost finished. We will have to exchange notes on any issues encountered with UT71 and Microdos. 

On Feb 20, 2020, at 3:59 PM, taf123 wrote:

Hi -

I've populated the board and set the jumpers in UT71 compatible mode.

<20200220_214602 _800x600_.jpg>


All ready for testing.

Well, not quite yet, I need to update some wiring on some of the other boards first.  but I'm so close, I can taste it.

Re: Todd's ELF-ish to get an FDC #Homebrew #microboards

taf123
 

Hi -

I've populated the board and set the jumpers in UT71 compatible mode.




All ready for testing.

Well, not quite yet, I need to update some wiring on some of the other boards first.  but I'm so close, I can taste it.

Re: Another CDP 1861

Jeff Truck
 

Regarding this quest for an 1861, are we pursuing the 1861 because of a firm hardware requirement or perhaps nostalgia?  

I implemented a video card for my Frankie system based mostly off of the VIP2K circuitry. I find the 4MHz speed of Frankie and the 192x192 resolution better than what I get on my SuperElf which uses the 1861.   

The only drawback I’ve faced is that programs written for the 1861 may require adjustment for the different resolution and video address space.  

Jeff 

Jeff

Re: Another CDP 1861

Stan Spielbusch
 


Another one (they go quick!)
https://www.ebay.com/itm/193351043540

Also have several other 18xx chips listed -- 1862, 1823, 1824, 1853, 1854, 1856, 1858, 1859, 1863, 1867, 1868, 1869, 1871


On 2/19/2020 1:36 PM, taf123 wrote:
Not any more.  Thanks!

Re: Another CDP 1861

taf123
 

Not any more.  Thanks!