Hi, I have a project that uses a Mega 168A. I developed on a MEGA168 and everything worked fine. I switched to a Mega168A because money, and now the code is broken. It appears one of my 2 ADC inputs is getting corrupted somehow. Maybe a timing issue with the mux? I am using interrupts to read the ADC results and a software timer to start the conversions.
Are there any differences between the 168 and 168A that would cause this?
-t-i-m-b-o-
Not really. I suspect that the system clock of the new Mega168A is different from the previous 168. These ICs come from the factory with the internal clock (8MHz) enabled and the Divide-by-8 fuse activated (logic low). Here the term "fuse" refers to internal 1-bit non-volatile configuration settings of the AVR. The fuses can be changed with an ISP programmer; even a USBasp module board that sells for a few dollars on eBay will work OK. For the USBasp, you will need to install a driver for Windows and for Windows 10, you also need to turn off the Driver Signature Verification in order to install this driver. Google for gory details.
Atmel have an app note about 168 to 168A transition. AFAIK it's simply a die shrink because they switched fabs and hence fab geometry. I think the note will tell you that A is a little more susceptible to noise. (smaller geometries always tend to be).
This very old post might have a few tidbits of info..the chip itself should match up good. They recommended just calling it a mega168..not sure if any of this still applies or applies to you
https://www.avrfreaks.net/forum/atmega168-vs-atmega168a-compilationexecution
Have you checked the migration app note?
http://www.microchip.com//wwwAppNotes/AppNotes.aspx?appnote=en591126
And the datasheet:
Although this may not apply to your app.
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I am using studio 7 and have set the fuse bits to disable the divide by 8 and to enable the external crystal.
I cannot find that app note. Number?
I am not using the ACME bit, but thanks for trying!
Found it! Thanks!
I linked to it in #5
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"Experience is what enables you to recognise a mistake the second time you make it." "Good judgement comes from experience. Experience comes from bad judgement." "Wisdom is always wont to arrive late, and to be a little approximate on first possession." "When you hear hoofbeats, think horses, not unicorns." "Fast. Cheap. Good. Pick two." "We see a lot of arses on handlebars around here." - [J Ekdahl] |
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