Some languages are versatile – I’ve found PHP to be nice for web dev, but dang, it’s memory representation of some structures is gross.
ATMEGA WAKE FROM DEEPSLEEP PIN INTERRUPT CODE
Poorly written OOP code can chew through memory.
ATMEGA WAKE FROM DEEPSLEEP PIN INTERRUPT PC
Things improved with the x86, though having gotten used to writing compact code, all that extra memory often went unused (often, one used extra memory to buffer things for increased performance, but because every PC had a different memory config, apps needed to run on the lower configs if you wanted them to be usable by a large audience).ĭespite developing using higher level languages (C, C++, Perl, Ruby (ugh, did I just vomit a little?), etc) for most things these days, memory consumption still remains important. I started programming in assembler on Z80 (CP/M) followed by 6502 CPUs (Apple and Atari), and there you had at best 64KB of memory total for the entire system, including the OS (and the ROM). Doing so, you easily visualize how much some changes add to your code size, and that helps a lot when you’re working with limited program space. See the code in Determining the delay and number of iterations Using an int before entering the loop avoids that,Īs I develop a programs, I test the builds and note the build size (for a given target, so size is apples-to-apples: if you change uC targets, binary sizes can change significantly), then note these either within comments within the module, or in the git commit comments (changes are pushed to a git repo regularly). Long math is slow enough that even on an 8MHz (no external crystal necessary) ATTiny8x, driving a pin high, delaying a fixed time (with delaymicroseconds()), driving the pin low, delaying, and doing long math to decrement a counter in a for loop results in a noticeable “click” in the output. This won’t be quite as precise, but for most purposes (“wait ‘x’ seconds before re-arming”), is more than sufficient, and the memory saved on the uC can be used for something more critical. Other examples include LCD (quite piggy), random (brings in 700-900 bytes of overhead, which makes it almost unusable on an ATTiny2x with just 2K of flash, but for “random-ish”, there are other things you can do that aren’t as costly), long and floating point operations (which can sometimes be circumvented by changing how you perform math operations and what sort of precision you really need), and delay().ĭelay brings in about 200 bytes of timer code that you can save by doing the following: On uCs with limited memory, it is not uncommon to need to forego the complete library implementation of something and raid the library for the minimalistic functionality necessary to accomplish the needed task.
PCMSK &= ~_BV(PCINT4) // Turn off PB4 as interrupt pin To handle this, I simply add these additional statements below their near twins: PCMSK |= _BV(PCINT4) // Use PB4 as interrupt pin One additional comment: in my actual program, I will need to awake if either of two buttons is pressed. This is called when the interrupt occurs, but I don't need to do anything in it PCMSK &= ~_BV(PCINT3) // Turn off PB3 as interrupt pin Sleep_enable() // Sets the Sleep Enable bit in the MCUCR Register (SE BIT) Set_sleep_mode(SLEEP_MODE_PWR_DOWN) // replaces above statement PCMSK |= _BV(PCINT3) // Use PB3 as interrupt pin GIMSK |= _BV(PCIE) // Enable Pin Change Interrupts Flash quick sequence so we know setup has started
When the button is pushed, it awakes, flashes the LED once and goes back to sleep. It then sets up for sleep mode and goes to sleep. It flashes the LED quickly to let you know the program is started.
However, there was enough here for me to figure out the problem and get it running. Unfortunately, even after reading through the forum thread the final working code was evidently never posted. So I’ll document my test code in case anyone else goes searching for a simple example. I spent an inordinate amount of time trying to figure out how put my ATTiny85 to sleep and then wake it up when the state of a pin changes.
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