| naikrovek | Posted: 11 May 2021, 03:20 PM |
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 Member Posts: 2 Joined: 11-May 21 |
Hi - I read somewhere on this site a few weeks ago that this is due to a clock drift between the GPS module and the ATTiny. I concur that this is the issue, as simply bringing my hand close to the ATTiny quickly fixes the problem for many seconds. I'm fortunate that I have a tall and thin cable modem which generates heat and which balances the clock perfectly, with the heat passing up and past the CPU - this fixes the problem. Is there a firmware fix for this so that I can place the clock in a less precarious position, or should I just install the 8MHz crystal and load capacitors? I have no complaints about this little hiccup, by the way. I've had the clock for weeks and am happy with it, and I love fixing little things like this. In my view, it's not a kit unless there's a problem you have to solve to make it work properly. I have a MiniPRO programmer and can reprogram the ATTiny relatively easily. I don't have an 8MHz crystal so I'm hoping there's a software fix. Thank you! ------------- |
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| mit | Posted: 11 May 2021, 05:03 PM |
 yeah whatever Admin Posts: 538 Joined: 4-May 16 |
Hi, I'd advise against fitting the crystal unless absolutely necessary, but if you do you'll need to reprogram the ATtiny fuse bytes to accommodate. Instead the problem can be solved by changing the oscillator calibration. The ATtiny reads a calibration byte from its internal EEPROM at address 0. The first thing to do is use your programmer to read out the EEPROM data as it is now, and take note of the first byte. Then, you can try writing a new value there, and rebooting the clock to see if it's any better. Here are two figures from the ATtiny2313 datasheet:   The graphs are inexact but they show the trend. If warming the chip fixes the problem, then I suppose the oscillator must be running slow, so you'll probably want to try a slightly higher value. Give it a shot, if you end up bricking it or run out of effort I can always recalibrate one here and post it to you. ------------- |
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| naikrovek | Posted: 11 May 2021, 07:22 PM |
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Member Posts: 2 Joined: 11-May 21 |
69 -> 6A seems to have fixed it. Thank you very much. Last edit by naikrovek at 11 May 2021, 07:40 PM ------------- |
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