Pin connector layout for original Gotek LED 7-segment?

for all subjects/topics not covered by the other forum categories
Post Reply
User avatar
sweh
Posts: 2262
Joined: Sat Mar 10, 2012 12:05 pm
Location: New York, New York
Contact:

Pin connector layout for original Gotek LED 7-segment?

Post by sweh » Thu Sep 03, 2020 3:21 am

I replaced the LED with an OLED and that seems to be working well (except I made the hole too large, so it's not very pretty).

Just for randomness I thought I'd try playing with the old LED on an Arduino (well, ESP8266).

But stupid me forgot to note what pins were what on the JP1 connector.

And I can't seem to find this information on google, anywhere.

Does anyone know what are VCC, GND, SDA, SCL ?

Thanks!
Rgds
Stephen

User avatar
MartinB
Posts: 5340
Joined: Mon Mar 31, 2008 10:04 pm
Location: Obscurity
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by MartinB » Thu Sep 03, 2020 9:42 am

Hi Stephen - I don’t know if the Micro-Gotek that I have uses the same bits and pieces but in the picture below, Blue is SDA, Green is SCL, Yellow is Vcc and Orange is GND and those are top to bottom on the display module.


497A84C5-C78F-4949-97FF-77C62B8B7928.jpeg

By the way Stephen, if you’re messing with I2C gadgets, you should be using my I2C rom on your Beeb, not that totally non-retro Arduousdino nonsense..... [-( :wink:

User avatar
sweh
Posts: 2262
Joined: Sat Mar 10, 2012 12:05 pm
Location: New York, New York
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by sweh » Thu Sep 03, 2020 11:13 am

MartinB wrote:
Thu Sep 03, 2020 9:42 am
Hi Stephen - I don’t know if the Micro-Gotek that I have uses the same bits and pieces but in the picture below, Blue is SDA, Green is SCL, Yellow is Vcc and Orange is GND and those are top to bottom on the display module.
Thanks, but that's the OLED board. They're nicely labelled and I have that working just fine.

The board I'm trying to understand is the 7-segment version, which has a header JP1 but the pins are unlabeled
Attachments
gotek-3-digit-led-lcd-display-screen-900x600.jpg
Rgds
Stephen

User avatar
MartinB
Posts: 5340
Joined: Mon Mar 31, 2008 10:04 pm
Location: Obscurity
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by MartinB » Thu Sep 03, 2020 11:20 am

Ah, ok Stephen. Is there another chip on there besides the 3-digit display? The latter modules don’t normally have I2C built-in.

User avatar
IanS
Posts: 1407
Joined: Mon Aug 31, 2009 7:02 pm
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by IanS » Thu Sep 03, 2020 11:26 am

From pictures on the web the driver is a TM1651
http://aitendo3.sakura.ne.jp/aitendo_da ... 1.1_EN.pdf

User avatar
sweh
Posts: 2262
Joined: Sat Mar 10, 2012 12:05 pm
Location: New York, New York
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by sweh » Thu Sep 03, 2020 11:39 am

MartinB wrote:
Thu Sep 03, 2020 11:20 am
Ah, ok Stephen. Is there another chip on there besides the 3-digit display? The latter modules don’t normally have I2C built-in.
Yeah there's a chip on the back. It's hard to make out the markings, but I _think_ it's a TM1651.

Since there's only 4 pins on the header and these plugged into the same connectors on the Gotek that the OLED does, it seems reasonable to assume the 4 pins are VCC/GND/SDA/SCL... but I don't know which are which, since they're unlabeled.

I was just hoping someone else who had upgraded their Gotek might have been smarter than me and noted what pins went where :-)
Rgds
Stephen

User avatar
MartinB
Posts: 5340
Joined: Mon Mar 31, 2008 10:04 pm
Location: Obscurity
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by MartinB » Thu Sep 03, 2020 12:02 pm

I realise you were hoping for the quick answer but I was thinking perhaps you could buzz out the pin connections knowing the interface chip and Ian has posted the pinout. If no answer is forthcoming, you can perhaps do that.

User avatar
sweh
Posts: 2262
Joined: Sat Mar 10, 2012 12:05 pm
Location: New York, New York
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by sweh » Thu Sep 03, 2020 12:48 pm

MartinB wrote:
Thu Sep 03, 2020 12:02 pm
I realise you were hoping for the quick answer but I was thinking perhaps you could buzz out the pin connections knowing the interface chip and Ian has posted the pinout. If no answer is forthcoming, you can perhaps do that.
That's not a bad idea; maybe I'll try it tonight and see what I can find. I'm so glad I bought one of those cheap head worn lighted magnifiers. My eye sight is getting to the point where I can't focus at that distance anymore!
Rgds
Stephen

User avatar
MartinB
Posts: 5340
Joined: Mon Mar 31, 2008 10:04 pm
Location: Obscurity
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by MartinB » Thu Sep 03, 2020 9:03 pm

Found this Stephen, see bottom left.....

9CAA87E5-2FC4-4470-A216-04B894AF4A57.jpeg

User avatar
sweh
Posts: 2262
Joined: Sat Mar 10, 2012 12:05 pm
Location: New York, New York
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by sweh » Thu Sep 03, 2020 10:01 pm

Thanks. But unfortunately there's no markings on the JP1 so I don't know what 1/2/3/4 are. I can make a guess on 1/2 based on the existence of the capacitor but...

So I took your idea and just played with a ohmmeter. Gnd was easy; it's the only one that gave zero resistance. VDD gave zero resistance on one pin and high (but not infinite) on the other 2, so I assume some pathway through the chip was occuring. But good enough.

This is what I ended up with:
jp1.png
Now to test it and hope I didn't destroy the board in an earlier test (where it got real real hot so I guess I did it wrong!).


EDIT: OK, I got the board doing something. I don't think it's i2c protocol but a dumber serial protocol. I need to understand the programming a bit more before I can it to display more than one digit at a time :-)

EDIT 2: Success! I've created a simple counter.

EDIT 3: OK, it's definitely not i2c but has some similarities. For example, there's no address frame. Transmission is done during clock low

The protocol appears to be:

"start" is triggered by SDA going from high to low while SCL is high. So: SCL high, SDA high, pause, SDA low, SCL low, pause.
"stop" is triggered from SDA going from low to high while SCL is low. So: SCL low, SDA low, pause, SDA high, SCL high, pause.
Data is sent similarly to i2c, with an ACK at the end of each byte.

So this seems to work. Initialisation is:
start: 0x8c: stop <-- turn LED on brightness 4 (0x80==control display; 0x08==display on; 0x04=brightness)
start: 0x40: stop <-- write mode

Now to display a number:
start: 0xc0, char1, char2, char3, 0x00: stop (0xc0 is "starting at address 0 (first 7-segment)"; the fourth 0x00 is 'cos the controller can do 4 segments)

Each byte written is:
For all 8 bits: SCL low, pause, SDA (high or low), pause, SCL high, pause
SCL low, pause, check ACK

And thats about it.

Now the "dot" doesn't seem to work as expected. It'd normally be 0x80 for each digit, but that doesn't seem to work. Instead if the fourth byte is 0x08 then dots 2 and 3 light up. I dunno what's up with that!
Rgds
Stephen

User avatar
1024MAK
Posts: 10292
Joined: Mon Apr 18, 2011 5:46 pm
Location: Looking forward to summer in Somerset, UK...
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by 1024MAK » Fri Sep 04, 2020 7:35 am

The chip only has seven LED segment drivers, normally the decimal point would be driven by an eighth segment driver. But it appears some kind of hack has been used by using the fourth digit feed and by the looks of it, the ‘D’ segment driver.

Mark

User avatar
1024MAK
Posts: 10292
Joined: Mon Apr 18, 2011 5:46 pm
Location: Looking forward to summer in Somerset, UK...
Contact:

Re: Pin connector layout for original Gotek LED 7-segment?

Post by 1024MAK » Fri Sep 04, 2020 9:08 am

50202A7A-40F1-4E5D-BAC1-FF288B073B31.jpeg

Post Reply

Return to “off-topic”