HxC Write Support Mod Help

SkydivinGirl

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I would really like to do the HxC Rev B Write Support Mod but I'm not exactly sure which parts I need to purchase. I was hoping one of our wonderful electronics geniuses here could perhaps supply us with a part number list or some other assistance.

Here's what's is required:
22/08/2010: Firmware SD HxCFloppyEmulator v1.3.0.0
- Amiga Write support added :

Note to the Revision B PCB owners :

To activate this new features you need to add a Microchip 23K256 SPI SRAM chip and 4 resistors.
The connection to do is :

23K256 pin 1 -> 220ohms resistor -> PIC18F4620 pin 22
23K256 pin 5 -> 220ohms resistor -> PIC18F4620 pin 27
23K256 pin 6 -> 220ohms resistor -> PIC18F4620 pin 28
23K256 pin 2 -> 220ohms resistor -> PIC18F4620 pin 29
23K256 pin 8 & 7 -> VCC3.3V (this voltage can be found at the capacitor under the sdcard connector or at the output of the regulator)
23K256 pin 4 -> GND
23K256 pin 3 -> Not connected.

(a 100nF capacitor is also recommended at the pin 8 of the 23K256)

After this modification you should see the message "SRAM OK" at power
There are about ten different versions of the Microchip 23K256 SPI SRAM chip but I'm guessing any one of them should work; it just depends on the type of mount (surface, through-hole, etc). I would like to stick with SMD components and mount everything on the board. That being said, I don't have a clue which resistors or capacitor to get. Can someone please help?!?!

Thanks!

Heather

*EDIT* I'll probably be ordering from Mouser so part numbers from there or the manufacturer would be great!
 

rkauer

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4 units of 220 Ohm with the lesser dissipation you can find (prefer common through-hole pieces 1/16 W) and one 100nF capacitor.
 

SkydivinGirl

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:blink: I really did not understand any of that except for through-hole and 1/16 W. If I search for that, there are hundreds of resistors. Searching for 100nF capacitors is also unintelligible to me.

Thanks!

Heather
 

rkauer

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Lesser dissipation = smallest size you can find.

Capacitor: any type you can find. Prefer the most sturdy one you can find, like the ones used in A500/A2000 boards.
 

Zetr0

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well I couldn't find the SRAM at Mouser so I had a look at Digikey for you.

Now I am unsure if you need a through-hole or SMD based component - so heres is a list -

The resitors are quite easy to get...

220 ohms is all you need (4 of them to be precise)

Also a 100nf (0.1uf) radial ceramic cap is easy to find on mouser

Now, I dont know the exact pitch you need for the packages so check the HxC as a reference. - also check that the 0.1uf cap is radial and not mono as I dont know for sure either =)

good luck and enjoy the hackery
 

SkydivinGirl

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Thanks Rogerio and Keith. I really appreciate the information.

@Zetr0 I was hoping to do everything with SMD components in order to mount the entire contraption on the existing board. What's the difference between a radial and mono cap?

Thanks!

Heather
 

Zetr0

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Hello Heather

Radial (and Axial) denote that a capcitor have a polarity, monolithic (mono's) capacitors do not.

axial-radial.jpg


Unless we are dealing with solid state capacitors - electrolytics have an aquaious liquid called an electrolyte - usually sodium hydroxide or other ionic solution.

Now, with the HxC I would have an educated guess that it uses a 0.1uf (100nF) monolithic - ceramic based capacitor but double check this first.

also - what pitch do you want the SMD based stuff in there are a couple to choose from pending on how small you want to go..

personally I wouldn't do anything smaller than 805

SMDsizes.jpg


603 without a placement tool is a nightmare to be honest... using tweasers will give you a head ache as you watch the little bits of cabon fly out at mach 2 on the carpet never to be seen again....

I do go on a bit (sorry about that) but hope that lot helps.
 

fatbob_gb

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No need to worry about "going on a bit", you may think that what you say is obvious but I for one welcome all the information that I can get about these things.

I am planning to do the same thing to my HcX and you have not necessarily answered all of my questions but have at least pointed me in the direction of what questions I need to be asking.

Thanks.
 

SkydivinGirl

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Thank you so much Keith! That was some very helpful information. :D I'll contact someone at the project to make sure the capacitor is monolithic then I should have enough info to get started. :D I'll be sure to post pictures when I start the project.

Thanks!

Heather
 

rkauer

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There are no polarized (with an electrolyte) capacitors on the 100nF range (or with less than 470nF, for that matter), they are all monolithic.
 

Zetr0

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@rkauer

thats a very good point hand't thought of that.

although there are polarized ceramics - like the lovely (explosive) tantalum capacitors... if you get that orientation wrong they fly off the board like pop-corn =)
 

SkydivinGirl

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Hi everyone!

I'm finally getting around to upgrading my two Rev. B HxC devices to have write support! I've got all the parts and I pretty much know exactly how it goes together, except for one thing. The information states "(a 100nF capacitor is also recommended at the pin 8 of the 23K256)". What I don't understand is if the capacitor goes between the 3.3V power and Pin 8. That's how I interpret it, but I don't know for sure!

I'd really appreciate someone's input on this before I move forward because I don't want to destroy my HxC. :)

Thanks everyone!
 

javidoom

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Hi!

I remember when Jeff made the mod, and I made "online" the first test :)

It was time ago, and I don't remember very well how I did it, but you can look at the thread in the official forums here:

http://torlus.com/floppy/forum/viewtopic.php?t=424

If I remember correctly, the very first firmware had an error and he modified it to make it work.

Some pictures in the thread too.

Regards.
 

fatbob_gb

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I think this image from the original forum posts shows that the capacitor should go between pin 8 and gnd (pin 8 is also connected to +3.3v)
 

SkydivinGirl

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Thanks for the info everyone! The only thing I don't understand is why the capacitor is just sitting between ground and the 3.3V. What's the purpose? Is it somehow taking a bit of power away from the chip or is it boosting it or what? Sorry, I'm still an electronics theory newb. :)

Heather

---------- Post added at 16:06 ---------- Previous post was at 16:02 ----------

I think I found the answer for myself. It's a Bypass Capacitor for removing voltage fluctuations. :)

Thanks again everyone!

Heather
 

SkydivinGirl

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When I decided to work on the HxC Rev B to Rev C mod today, I saw a few different examples of how people connected the parts to the HxC. Out of the ones I saw, two really stood out to me.

The first was the mod from mfilos. He had everything nicely arranged on a project board then routed the wires through one of the mounting holes he was not using. I liked this method because the bottom of the board looked nice and tidy and the add-on board could be fairly hidden under the LCD.

The other one I really liked was one I saw on an HxC that our own fitzsteve sold. I really don't know who did the mod, but everything was mounted directly on the bottom of the board.

Out of the two, I decided to go with the bottom mounted method. The only problems that I saw with the one fitzsteve had were that it was missing the capacitor and there were a lot of bare chip and resistor legs that could possibly short circuit. So, after getting some great advice from my fellow Amibayers about connecting the capacitor, this is what I came up with.

First, I had to bend all the legs on the chip so they were horizontal to the chip. The only exception was pin 4, which is ground. I then snipped off the thin part of each leg because they were too long. The capacitor needed to go from ground then connect to pin 8 so I thought the best way would be to connect it directly to the chip then go over top to pin 7 and 8.



Next, I added all the other components (4 Resistors + 1 Wire for Power) to the chip. I did all of this on the chip itself, without attaching anything to the board. I found this to be nice because all the difficult work is done before you start soldering on your precious HxC. :)

It was very important to me to keep the possibility for shorts to a minimum, so I used heat shrink tubing to cover as many connections as I could. The power wire, the other end of the capacitor, and pins 7 + 8 are all soldered together.



And finally, the easy part. Pin 4 of your mod sits in a hole that's just above pin 22 on the bottom of the HxC. Remove the PIC to solder this pin to the board. This gives the mod a nice solid connection to the board. From there it's just a matter of cutting down the resistor legs and soldering them. Run the power wire and it's all done!



Works a charm and it's nice and compact. Thanks again to everyone who helped me figure out the parts I wasn't sure about. I've got another Rev B that will be going under the soldering iron tomorrow. :)

Heather
 

mfilos

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AWESOME pr0n pics!!!

Thanks for sharing Heather! Pro mod :)
 

SkydivinGirl

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Thank you! I'm learning a lot from every project I do. It's a lot of fun. :)

I finished the mod on my other Rev B HxC today. It works just as it should.



Now it's time to add a rotary switch to my 64NIC+. It's just six solder points so it will be quick. Fortunately, I have plenty of projects to work on. :D

Heather
 
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