| nathan | Posted: 29 Oct 2021, 01:31 AM |
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 Member Posts: 7 Joined: 29-October 21 |
Images: https://drive.google.com/file/d/1szfNyKHhGyGdXCvY3aZC26Ahlk-ugQq8/view?usp=sharing I double checked the solder connections and they all look connected. Disclaimer: I am new to soldering.  ------------- |
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| mit | Posted: 29 Oct 2021, 10:01 AM |
 yeah whatever Admin Posts: 538 Joined: 4-May 16 |
Do you have a multimeter? If nothing lights up at all, the first step would be to see if the power supply is OK. At the barrel jack, it should be possible to read a 5V across the pins. There is a tiny LED on the GPS module itself, does that light up? If you can take some more pictures, close up of the solder joints, it might help me spot problems. ------------- |
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| nathan | Posted: 1 Dec 2021, 08:12 PM |
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Member Posts: 7 Joined: 29-October 21 |
Close up on all the connections: https://photos.app.goo.gl/exY7m7G83hP3ZR4Q7 I tested the cable directly with the multimeter and got 5.1V However, when I plug in the barrel and read on the outside connection I only get 1.7V. (Got zero volts on the other connector, assuming it's ground or something) Pictures of what I mean attached   (Thank you for the patience, had to wait for family) ------------- |
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| mit | Posted: 2 Dec 2021, 01:37 PM |
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yeah whatever Admin Posts: 538 Joined: 4-May 16 |
Hi, looks like your ATtiny chip is mounted in the socket backwards. There is a small D-shaped cutout at one end of it, that needs to match the white outline on the board. It might be enough to just remove the chip from the socket and turn it around, but it's possible the chip has suffered some damage, if that's the case then I can send you a new chip. ------------- |
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| nathan | Posted: 3 Dec 2021, 04:10 AM |
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Member Posts: 7 Joined: 29-October 21 |
Awesome, that made the clock boot up! However, I have two other issues: - Time is just counting up from zero. The GPS Fix LED on the back is flashing. I have left it for ~40 minutes, and will also leave it overnight. According to the guide, there was an issue with the Attiny chip a year ago, so maybe the fault is in the same spot. The light on the gps module itself stays on most of the time, but it briefly flashes off at the same time the GPS fix light flashes. - Centiseconds (last digit) is not getting any power. I re-soldered it and it looks good enough, still no output though. Is it safe to check the pins with a voltmeter? If so, which ones should I check? ------------- |
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| nathan | Posted: 3 Dec 2021, 03:29 PM |
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Member Posts: 7 Joined: 29-October 21 |
Update: Almost 12 hours with no reception. Is there a way to know if it's the module's fault or the antenna's fault? ------------- |
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| mit | Posted: 3 Dec 2021, 05:22 PM |
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yeah whatever Admin Posts: 538 Joined: 4-May 16 |
Ah, I'm glad the ATtiny chip is OK. The GPS fix LED is flashing, that means the GPS module is all OK and working. There is probably a soldering error somewhere between the GPS module and the ATtiny. This could be at the base of the GPS module (which is quite hard to investigate) or at the legs of the ATtiny socket (which is also hard to investigate). You can try investigating further with the multimeter in continuity-tester mode. With the clock turned off, see if there is continuity between the middle pin on the GPS module (TXD) and pin 2 of the ATtiny - here's a picture with pin 2 highlighted:  The same goes for the centiseconds digit. The problem might be at the legs of the digit, or at the other end where the cathode is connected to the display driver. The cathode for the centiseconds is connected to pin 2 of the MAX7219 display driver, highlighted again:  ------------- |
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| nathan | Posted: 3 Dec 2021, 07:59 PM |
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Member Posts: 7 Joined: 29-October 21 |
I checked and the TXD and ATtiny pin 2 have continuity. I think the centiseconds digit isn't working because some of my LEDs aren't connected. (I messed up a bit when soldering them, so I removed them). I bought some more red ones that are 2.0-2.2V, will those work fine? (Thanks for all this help, you're awesome) ------------- |
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| mit | Posted: 5 Dec 2021, 05:30 PM |
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yeah whatever Admin Posts: 538 Joined: 4-May 16 |
The LEDs are driven with constant current, so those should be fine, although they might not match the colour of the others exactly. Not fitting the colon LEDs shouldn't stop the digit from working, unless perhaps the colons are shorting the signal. Certainly worth trying to get those working. When the clock gets a GPS fix, it flashes the colons. It would be useful to know if the colons do start flashing in this case, even if it doesn't display the time. It might be worth trying to read the serial data with a usb-serial adapter, that would usually be my next step in debugging. Can I ask when was this kit acquired? As of about six months ago I have been testing every GPS module before shipment, but before that very occasionally there were problems with some modules. Just once I had one power up at the wrong baud rate, whereas they're always supposed to initialize at 9600bps. There was also the problem of the NMEA messages starting with $GN instead of $GP, but the firmware was patched to accept both last year. ------------- |
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| nathan | Posted: 6 Dec 2021, 12:37 AM |
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Member Posts: 7 Joined: 29-October 21 |
The colons start flashing after a minute or so. We bought the kit around September this year. ------------- |
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| mit | Posted: 9 Dec 2021, 04:40 PM |
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yeah whatever Admin Posts: 538 Joined: 4-May 16 |
Sorry for the delay. The GPS unit is most likely fine. And if the colons start flashing, that means the PPS signal is fine too. If there really is a good connection between the module's TX and the ATTiny's pin 2, then it might be that the ATtiny suffered some damage when it was powered up in reverse. It's possible the EEPROM got erased (which would only affect the oscillator calibration) or simply that the part heated up and altered the characteristics of the RC oscillator. I think it might be worth trying a new ATTiny chip, which I could calibrate and send to you if you email me. ------------- |
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| nathan | Posted: 10 Dec 2021, 01:48 AM |
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Member Posts: 7 Joined: 29-October 21 |
I just sent an email :) ------------- |
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