Timeline for Smaller and cheaper alternative to Arduino Uno for permanent projects
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
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| Dec 7, 2019 at 15:50 | comment | added | raddevus | @Kavka That's great information. Thanks for adding. | |
| Dec 6, 2019 at 16:03 | comment | added | anon | @reddevus. To be more precise, the crystal that you indicated in the red box in this answer is the crystal used by the microcontroller handling the USB communication, and not by the ATmega328p-pu chip. You can see from the Uno schematics that the ATmega328p-pu chip actually uses a resonator: mouser.com/ProductDetail/Murata-Electronics/… | |
| Nov 13, 2018 at 0:43 | comment | added | Rudy | Why is there no bypass capacitor on the power pins in the breadboard picture? That is an absolute must. As close to Vcc and Gnd as possible. Hey, but it is the Internet. Anyone can publish what they want. | |
| Nov 12, 2018 at 21:56 | vote | accept | Andy | ||
| Nov 12, 2018 at 20:45 | comment | added | raddevus | @duskwuff Thanks for the enlightening discussion. I agree with what you are saying and will change my docs and circuits soon to insure that is always connected. FYI - I started working with ATMega328p-pu via the fantastic book AVR Programming : Learning to Write Software For Hardware (amzn.to/2PS9OOA) and in those first circuits the author, Elliott Williams, does not hook up those pins either. I think I was influenced by that. The book really is great though and the author is knowledgeable. Thanks again, great discussion. | |
| Nov 12, 2018 at 20:01 | comment | added | user7800 | @raddevus Again, table 28.8 specifies an "absolute min/max" voltage. Absolute limits always carry an implied risk of damage if the limits are violated. | |
| Nov 12, 2018 at 19:35 | comment | added | raddevus | @duskwuff also section 1.1.7 says, "AVCC is the supply voltage pin for the A/D Converter, PC 3:0, and ADC7:6. It should be externally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter." Notice the use of should instead of must. Interesting. | |
| Nov 12, 2018 at 19:27 | comment | added | raddevus | @duskwuff I was reading over the datasheet and reminding myself too. I will keep that in mind and alter the doc soon. Thanks Edit - Wait where does datasheet say that leaving AVCC unpowered may cause damage? | |
| Nov 12, 2018 at 18:55 | comment | added | user7800 | @raddevus Refer to Table 28.8 in the datasheet: "AVCC absolute min/max: 1.8V/5.5V". Leaving AVCC unpowered is out of spec, and may cause damage. The GND pin on pin 22 isn't specifically associated with the ADC, and must be connected to GND. | |
| Nov 12, 2018 at 18:47 | history | edited | raddevus | CC BY-SA 4.0 |
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| Nov 12, 2018 at 18:41 | comment | added | raddevus | @duskwuff, I believe that is only when you're doing DAC. This is just a simple example to get someone started in the direction of using the chip as standalone. I assure you the code to blink the LED in the sample does run. Also, when I was starting out I created the circuit I mentioned in a comment above and I never connected AVCC and GND and the circuit ran for two years. Of course, i'm not saying that will always be true. Just mentioning the way the chip actually works. As always, check the datasheet for exact specs and especially if you experience something different. Thanks. | |
| Nov 12, 2018 at 18:36 | comment | added | user7800 | You're missing a few wires in that last photo. Pins 20 (AVCC) and 22 (GND) need to be connected to VCC and GND. | |
| Nov 12, 2018 at 18:18 | comment | added | raddevus | @SnakeDoc Thanks. And, I agree, any circuit protection is always advantageous. An interesting note: I had a circuit built on a cheap breadboard like the one shown, powered off an old phone charger and sitting on a shelf in my garage and running for over two years with no problems. We even had a lightning strike that took out another item in the garage but my atmega328p-pu based circuit (bluetooth garage door opener) kept on running. Of course, I'm not advising people to build circuits like that but it is really cool that as a hobbyist we can do things like this. | |
| Nov 12, 2018 at 18:09 | comment | added | SnakeDoc | You'd be well served to add some circuit protection in there, since the 328p doesn't have any of it's own. Otherwise, this is a great way to go. | |
| Nov 12, 2018 at 15:12 | history | answered | raddevus | CC BY-SA 4.0 |