Can the propeller run on 3.0 volts
dr hydra
Posts: 212
I know the data sheet shows a min of 2.6volts...but what happens if the voltage is 2.8 to 3.0...does the propeller run or does it keep resetting? Does it cause any damage?
Comments
If you disable brownout you can go as low as just over a volt, though various functions such as oscillators drop off on the way. See this thread
http://forums.parallax.com/showthread.php/129731-Prop-Limbo!-how-low-(power-voltage)-can-it-go!
You replied
So why do you start a new thread? We like to help but you aren't being very helpful yourself. Instead of asking confusing questions, just say what it is you are trying to do, add some context so we are clued in, mention any other relevant threads etc If we can go to the trouble of answering you then surely you can go to the trouble of taking a few minutes thinking about the question and providing sufficient details.
Going back to what I said in the other post I had mentioned that the "3V" is not nicely regulated since it goes through a Schottky whose voltage drop will depend upon current, so you can expect the supply to drop below the nominal "3V" and quite possibly trip the brown-out, or at least cause problems with running at 80MHz even. Go back to using a regulator and don't treat the forum as a vending machine, we are real people.
Table 6 lists some definitions for abbreviations used in Table 7; entries under "I/O structure" with a value of "FT" are 5v tolerant as an input. You would have to do some checks: figure out which pin name you're connecting to; determine its default state and function out of reset. Depending on those results, you may have to hold the Propeller in reset until the STM32 has started up and reconfigured any pins the Prop is connected to.
Diodes or current-limiting resistors shouldn't be required. Driving any Prop pin shouldn't be an issue.
I cannot find the default settings for the gpio pins...any ideas...once I found out the default setting...I need to make sure the gpio is set to input with no pull or pull down...correct. At that point the pin will be 5v tolerant...correct.. Or am I missing something
Most of the pin names are like "PA#", "PG#" and so on, so that would be the pin function after reset, but if it has something in parentheses listed also that is the function after reset. These are mostly the pins associated with JTAG / programming and debugging the STM32 so you should probably avoid them if possible.
Depending on what you're doing, you might have a need to set an input pull-up or pull-down, or might need an external up/down in some cases. For instance, if the STM32 has a pin that the Prop switches either LOW or HIGH for something to happen, if you enable the internal pull-up or pull-down, you won't have a floating signal there that could cause a false trigger if the STM32 starts up before the Prop starts.
This has been a big help...it looks like most pins are set floating input...which would make the ft pins 5v tolerant. Perfect...
I am thinking the safest setup for me would be to run the gpio input float on 5v tolerant pins with an external pull down...that should give me the 5v tolerances and avoid false reads on the input pins...that should work?
With a multiple MCU set up, you can sequence which MCU boots up first, so maybe consider one MCU is held reset until the other boots and then that one releases the other to boot.
You can go the other way, where if the Prop thinks the STM32 is doing something wrong, it can cause the STM32 to reset too, which would basically reset the whole system.
*to add- someone please correct me if I'm wrong.