Gotek schematics

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wastebeaker
Posts: 4
Joined: Mon Nov 28, 2016 1:48 pm

Gotek schematics

Post by wastebeaker » Mon Nov 28, 2016 2:00 pm

Hi folks.

I've been browsing and a-googling, and I thought I'd be able to fix this without bothering someone else but it appears it's inevitable. Considering there are several Gotek devices, probably someone else has encountered this problem, but I couldn't find it searching through the forum. If a solution is here, and I've missed it, I humbly apologize and would greatly appreciate a link to the relevant thread.

So, I bought a Gotek SFRC922B and thought hey baby it's gonna be great to get that old sampler working again, completely overestimating my own abilities as usual. I then bought an FTDI USB/TTL converter and borrowed the electronics lab at work, sat down to solder and realized my Gotek device is different from those in the pictures I've seen on various forums and youtube vids. Also, I can't find the relevant points (TX, RX, VCC3v3 ) on the Gotek device, while all the points are properly marked on the USB/TTL converter. I thought I'd just be a good monkey and follow the pictorial in this link: http://www.vogons.org/viewtopic.php?f=46&t=43416 but the pins/points that has been soldered here are in a different layout in my device, and they're not marked...

Is there some general information about where to find these pins/points on such devices I've missed out on? Or are the schematics of the Gotek device available somewhere?

Any help would be highly appreciated.

Edit: Added a photo comparing the 922 and 922B. Can I assume that the two top ports are 5V and GND and that the two directly beneath those are TXD and RXD? Doesn't really make sense, because what I've assigned as TXD is marked as RS.
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mondo1976
Posts: 156
Joined: Mon Dec 28, 2015 3:54 pm

Re: Gotek schematics

Post by mondo1976 » Thu Dec 01, 2016 8:10 am

You don't really need the schematics to the Gotek. Just use a continuity tester to find which header pins lead to which pin on the STM32 chip. The STM32 chip pinouts are published so they'll tell you which pin is TxD and RxD, and then the continuity tester will tell you which header pins correspond to the STM32 pins.

In other words, easiest way is to actually find TxD and RxD on the STM32 first and then try all 7 header pins until you find which pins match. STM32 programming isn't really my area of expertise, but I believe you'll be successful locating it this way:

With the Pin 1 dot of the STM32 in the upper-left corner, PA10 (RxD) should be the sixth pin down the right side and PA09 (TxD) is the seventh pin down the right side. RxD/TxD are labelled relative to the STM32 chip, not the programmer, so the TxD of the programmer should talk to the RxD of the STM32 and vice-versa.

Hopefully that makes sense.

wastebeaker
Posts: 4
Joined: Mon Nov 28, 2016 1:48 pm

Re: Gotek schematics

Post by wastebeaker » Fri Dec 02, 2016 2:44 pm

Thank you for your reply mondo1976, appreciate it:)

This sounds like a good idea. My experience with this stuff is extremely limited, just like my brain, so bear with me here. I've only used a multimeter before and 'continuity tester' is a bit unknown to me. It's a device used to put voltage on the selected points and detect if the current is going through a closed circuit? What constitutes a match then, if there is zeroish resistance in the circuit you closed? Then I could do this with a plain multimeter, right? Sorry if I'm not using the correct terminology, english is not my primary language :)

mondo1976
Posts: 156
Joined: Mon Dec 28, 2015 3:54 pm

Re: Gotek schematics

Post by mondo1976 » Fri Dec 02, 2016 6:25 pm

Yes, it just checks to see if there's a path of zero (or very close to it) resistance between two electrical points. It's pretty much the most basic feature of any multimeter so your meter should definitely have it, but of course you could even use an ohmmeter in the same way because a continuity tester is just an ohmmeter that signals when there is little to no resistance. Touch both probes together and the meter should buzz. Touch one probe to the end of a good piece of wire and the other probe to the other end the same wire and the meter should buzz. If the wire is broken somewhere, the meter won't buzz.

So all you will be doing with the Gotek is seeing which pin of the STM32 is electrically connected to which header pin. When the meter buzzes (because it can complete the circuit between the two probes) then you'll know those two points are joined together.

Easy solution.

wastebeaker
Posts: 4
Joined: Mon Nov 28, 2016 1:48 pm

Re: Gotek schematics

Post by wastebeaker » Sun Dec 04, 2016 4:55 pm

Hi again.

The chip is labeled as STM32F105 R8T6.

I located this document: http://www.st.com/content/ccc/resource/ ... 220364.pdf

Pinouts starts at page 24. I'm not sure I understand how to locate those pins. For example, the VCC3v3 is not listed in the first pictures and I can not find it in the pin description table below (starting on page 27), but it might be the one labeled Vbat (figure 4, page 26)?

"With the Pin 1 dot of the STM32 in the upper-left corner, PA10 (RxD) should be the sixth pin down the right side and PA09 (TxD) is the seventh pin down the right side". How do you know PA10 is RxD and so on?

If PA10 and PA09 are Rx and Tx and I have located +5v, GND and J3 then I just need to find VCC3v3 right?

Thanks for your help

mondo1976
Posts: 156
Joined: Mon Dec 28, 2015 3:54 pm

Re: Gotek schematics

Post by mondo1976 » Sun Dec 04, 2016 8:13 pm

In that specific document, your chip version should be page 26. The STM32 chip in your Gotek has 16 pins on each side, right? If it's STM32F105 RBT6 (like you said) then it should. Just double checking.

Starting from the left side on the top row of pins, Boot0 should be five pins to the right. Technically, it is Pin 60 and you'd count that counter-clockwise starting from Pin 1 which is the first pin at the top of the left side column of pins. But it's easier to find it as top row, fifth in from the left.

VCC3V3 can be found by testing for voltage** at the Gotek programming header pins. The reason you need VCC3V3 is to bring Boot0 high (to 3.3V) which puts the STM32 in a special mode.

** You could power up the Gotek with just the 4-pin power connected and nothing soldered to the programming header or otherwise connected.

Rx/Tx are used for serial communication between the STM32 and programmer (so it can send the new bootloader data, of course). Remember, the Tx of the programmer has to talk to the Rx of the STM32 and vice-versa.

GND and +5V can be matched to the 4-pin power header (center two pins are ground) and the +5V is clearly marked as the 4-pin power header pin that's closest to the center of the board (on the "bottom" in your picture).

This is just a guess, but looking at your 7-pin programming header pic, I believe the bottom right is RESET.

That eliminates three of the seven, so the remaining pins should be Boot0, +3.3V, Tx and Rx. Tx/Rx will be connected somewhere in the right side pins of the STM32. Boot0 is on the top row. +3.3v is second pin in from the left on the top row, I believe. Whatever header point you suspect is +3.3V (or actually measure it as 3.3V) should have continuity with that pin on the STM32, so verify that.

Keep in mind that I could be mistaken about some of this, so make sure you double (or triple) check all this stuff, and use your brain and logic. Common sense stuff, like TxD clearly isn't going to be connected to the 4-pin power connector, etc. If you notice anything inconsistent or something that doesn't seem to match up then take a step back, do some more research, and then come back to it.

Once you get it figured out 100%, please do post a labelled picture so anyone else will have an easy go at the problem.

SymphonicSamples
Posts: 1
Joined: Thu Feb 16, 2017 1:41 pm
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Re: Gotek schematics

Post by SymphonicSamples » Fri Feb 17, 2017 9:33 am

Hey , new to the forum so first up, hello :D Ok, so I just got my Gotek drive, opened it up and found it was the same PCB layout. Mine is a SFRC922C , so clearly they change the board layout from B onward. Anyway I just finished programming mine without any issues. Here's a picture of my board and the points I used just to help anyone else out.

Cheers

Image

cartoondonkey
Posts: 1
Joined: Tue Jul 25, 2017 11:23 pm

Re: Gotek schematics

Post by cartoondonkey » Tue Jul 25, 2017 11:25 pm

Hey can you send me your schematic, or a pic of your soldering points? Your image expired and I have this rev C board!

Vaklin
Posts: 26
Joined: Sun Jul 23, 2017 3:41 pm

Re: Gotek schematics

Post by Vaklin » Wed Jul 26, 2017 7:36 pm

Red - + 5V
Blue - GND
Yellow - data TO device (Computer TXd line)
Brown - data FROM device (Computer RXd line)

Closed jumper - bootstrap mode

Unused pin pinhole - reset (negative logic)
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Vaklin
Posts: 26
Joined: Sun Jul 23, 2017 3:41 pm

Re: Gotek schematics

Post by Vaklin » Wed Jul 26, 2017 7:43 pm

Schematic...
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