Timeline for Is there a way to play .mp3 files from an SD card on Arduino?
Current License: CC BY-SA 3.0
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| Feb 12, 2018 at 11:20 | comment | added | Michel Keijzers | @Majenko my initial plan was to store some arrays in external SRAM. That is easy to reference from a pointer stored in Uno's SRAM. However, I needed linked lists and lots of small objects, so it is too complicated. So what I intended was some kind of 'user made' MMU). A bit too much outside the scope of the project (which I still wonder if I will finish it, even on STM32). But meanwhile I learn a lot doing side tests for my hobby projects, also thanks to your comments (so thanks again). Sorry for thiss off-topic comments. | |
| Feb 12, 2018 at 10:50 | comment | added | Majenko | Yeah - the difference between page mapping (hardware implementation) and page swapping (software implementation). For the former you need the chip to have external memory in the first place, so you can switch in and out different physical banks of memory (like the C= 64, Spectrum +2/3, etc did to get round the 64k limit). For the latter the chip has to have an MMU or some similar form of page fault mechanism to implement a virtual memory map. Neither of those are available in the AVR... ;) | |
| Feb 12, 2018 at 10:47 | comment | added | user31481 | @Majenko. It look like the good old days with extended memory and expanded memory and all sort of trick around the 640KB barrier. | |
| Feb 12, 2018 at 10:46 | comment | added | Michel Keijzers | True ... that's also the reason I didn't use it in my project. Because i had to make my own 'memory map' from variables to external SRAM. For MP3, I thought it could be used to store a small chunk of decoded data and to process it to undecoded data. But yes, it will not be advantage for the limited CPU speed of a Uno anyway. | |
| Feb 12, 2018 at 10:42 | comment | added | Majenko | You're not adding memory to the Uno there - you're adding an external peripheral that happens to have memory. Adding memory to the Uno would entail including it in the memory map so you can use it for variables, etc - something the AVR doesn't support. Yes, you could offload some data into there for storage, but you can't process it while it's in there. It wouldn't just be slow - it'd be unusable for audio processing. Yes, the technology is SRAM, but in actuality it's more like an SD card or hard drive. | |
| Feb 12, 2018 at 10:40 | comment | added | Michel Keijzers | Note that it is possible to add memory to an Uno ... I did a test with a 23LC1024 and it worked. Slower than internal memory, but it worked. But I agree, the speed might be a problem too (that's why I made the time constraint remark). I don't know exactly what the requirements are for MP3 decoding, looks like more than the Uno can process. | |
| Feb 12, 2018 at 10:35 | comment | added | Majenko | MP3 decoder on an Uno...? I think not. Maybe on a Due (I ported one to the PIC32 for chipKIT a while back, and it kinda worked), but not an Uno. Not enough memory. I used to run MAD on a 25MHz Sun SPARC system, but that had megabytes of RAM, not a couple of kilobytes. For an Uno external hardware is a requirement, not an option. | |
| Feb 12, 2018 at 9:23 | history | answered | Michel Keijzers | CC BY-SA 3.0 |