HP97 The journey begins

[Jonas Sandstedt]

Sounds great, Tony!
In my world you are a real hero!
Now comes the big question- when will mass-production start ??
In any way, I want to order three kits.
Best regards Jonas

[teenix]

Hi Jonas,

Thankyou. Because of the calculator design, there is soldering involved with this model, so I'm going to ask anyone interested to download the CalCom zip file and read through the install notes in the 19C help file. It's not difficult but if it cannot be done, and if the bits can be sent to me, I'm offering to solder them.

I'm available on the email button.

cheers

Tony

[Jonas Sandstedt]

Sounds great, Tony!
In my world you are a real hero!
Now comes the big question- when will mass-production start ??
In any way, I want to order three kits.
Best regards Jonas

[Jonas Sandstedt]

Sorry, something went wrong and my post was re-posted. I will come back to you, I am checking Swedish import fees.
Best regards Jonas

[teenix]

Hi all,

I got my teeny, ooh was that a pun , Woodstock battery charge board today.

It all looks like it will fit. Dave (Dreato) has some of his USB Woodstock charger cables modified to suit so should work well with matching CPU board.

cheers

Tony

[zixingcheche]

Hi Tony

That is good news! Woodstock is coming...

BR,

[teenix]

Hi all,

I was trying out the new battery charger board with the HP-25 shell. The charger works fine with the LED going off after full charge.

The battery and charger fit quite nice into the original battery holder and the original spring holds it all snug. The challenge was that the battery and charger need 3 connections to the main CPU board.

This presented a problem because the battery needs to be removed as easy as the original and the flat surface of the spring-loaded battery connector will be happy with 2 pins even if the board sits at a slight angle, but with 3 pins, one might not contact properly. I solved this by using tiny pogo pins with spring loaded contacts.

The battery slips in and out easily and good contact is made.

The attached image shows this, albeit the soldering is a bit awful. It is hard to hold these slippery little pins while trying to solder so I'll have to make a small jig.

The image also shows Daves Woodstock charger plug in position. This connects 5V from the USB port direct to the battery charger and can power the calculator while on charge.

More to fiddle with yet.

cheers

Tony

[teenix]

Hi all,

I was fiddling with the Woodstock today and it would not work. Many frustrating hours later after I stripped the code down a bare bones program just to toggle a few output pins. These toggled ok but on the wrong pins. How could this be, I checked and re-checked the code, but no success.

It turned out that the manufactures data sheet had the processor pinout diagram drawn wrong. I mean really - this is a pretty important piece of information and can lead to damage. I usually check the device errata sheets, but I didn't think this type of problem would occur.

Now all the new circuit boards have to be scrapped.

Murphy strikes again :-(

cheers

Tony

[Dreato]

Man that's frustrating! If this happened to me, there would be cursing involved. Stick with it, Tony. We need you!!!

Regards,
Dave

[MinkLib]

Boy oh boy. My sympathies.
I assume it's a Microchip 18LF47K40 error, not HP/AMI from the Seventies :-)

Very glad a Teenix Woodstock is underway. Used an HP25 for stress calculations on my M.Sc. thesis at that time (the Seventies).

best wishes,
MinkLib.

[teenix]

Hi all,

While I wait for a few parts for 19C board, I put together the new Woodstock. I haven't tried it yet, so hopefully the latest data sheet was accurate this time.

As it is difficult to see when the battery is charging or charged with the battery setup, the PIC processor can now see this and indicate it on the LED display.

I added a port for a clock but with clocks everywhere these days, I'm not sure it is warranted.

The attached image shows the new board with the battery charger next to it. If it fires up, I'll plug in Dave's Woodstock USB cable to see if it charges properly.

cheers

Tony

[teenix]

I forgot to mention, I got my HP-91 and HP-92 board back too.

That's another story :-)

cheers

Tony

[teenix]

Hi all,

I had a bit of a failure with the motor drive for the 19C. It worked but was a bit too touchy when it came to changes in torque loading.

I changed the driver IC and it seems better, although I haven't energized the print head yet.

I thought maybe I could reverse track and try to mimic the original driver which was controlled by the motor back EMF and the PIK chip innards. This is a bit of a teaser because no-one really knows what is hidden in there. Anyway, I'm pretty sure I figured it out today and did a mockup circuit and after some fiddling with some logic, what do you know, it worked. The motor speed is adjustable just like the original with a trimmer potentiometer, plus it can be sped up easily for homing.

The only trouble is, just like I found out with the 97 printer, it too suffers a bit from motor torque changes and the print motor will change speed if it is loaded such as by applying a tiny bit of pressure to the print head as it is moving.

This setup also requires a few parts to work, so I am weighing up whether to just use the new IC I chose which is much more compact, and it only takes changes in software to change the motor operating characteristics. I have already compensated battery voltage changes and this driver seems "stiffer" than the other one I used, so I will see how the printer performs with it.

With the print motors having aged quite a bit now, plus mechanical wear, they might be a bit tired in some ways and might not perform as good as new anyway.

Either way, it was an interesting trip to delve a bit more into the PIK innards.

cheers

Tony

[teenix]

Hi all,

Just for interest, this is the circuit for the printer motor drive I was playing with. It works but I think it still has limitations, unless I did something wrong. It is quite simple in practice and requires no adjustment other than setting the speed with the trim pot.

It was based on HP Patent 3,976,926 and the HP-19C motor drive

cheers

Tony

[Paul Dale]

Great effort -- yet again.
You are doing a fantastic job of keeping these old machines more than alive.

Pauli

[teenix]

Hi all,

Progress almost came to a standstill. I was staying in a caravan to help my daughter out, but unfortunately, I was evicted because the owner wanted it back. The cheek of some people, it was only two years. ;-)) Mixed blessings though, it was really hot.

Anyway, finalizing the 19C came to a halt as I just don't have the space to keep it going at the moment. This should not be too long though. The good news, I am able to keep going on the Woodstock as it is only software. I have all the general software done for the processor and the PC, now I am just going to add a few goodies. The code so far has only used 45% of the ROM space so there is plenty available.

I added a clock with 5ppm accuracy and as there is limited space on the circuit board, it only has backup similar to the original Woodstock Continuous Memory. That is, if the battery needs changing or to do a hard reset on the processor, it can be removed for upto about 10 seconds and the clock data will stay active. The processor will fully shut down, but the actual continuous memory will hold up as long as it stays viable, which will probably outlast me.

cheers

Tony

[teenix]

Hi all,

I've just playing around with the Woodstock turbo mode.

In normal mode, it takes about 7 seconds to run a program that calculates SIN 45 10 times. In Turbo mode it takes a bit under half a second, so about 14 times normal speed.

cheers

Tony

[Paul Dale]

Nice improvement.

[teenix]

Well, it looks like the Woodstock code is done. There is plenty there including changes to the Windows interface and Emulator link, so I'm sure a bug will show up.

I've added 6 new program steps and as I have done in the past, the original Woodstock code is untouched.

I have been waiting for weeks to get a couple of parts to finish the power module but it seems like I've been dudded. I've got some that are suitable but not quite what I want so these will have to do to finalize the design and I'll find a different supplier.

cheers

Tony

[zixingcheche]

HI Tony
That is good news! looking forward to have one even two WOODSTOCK CPU!
Thank you!