You can absolutely make a c program from assembler. The problem is it may not look like what you are thinking, or maybe it will. My PIC is rusty but using another assembler, say you had add r1,r2 In C lets say that becomes r1 = r1 + r2; Possibly more readable. You lose any … Read more
Yes, volatile is required, and the right declaration is: volatile unsigned char *my_data; This declares my_data to be a pointer to volatile unsigned char. To make the pointer itself volatile, you’d need this instead: unsigned char *volatile my_data; And of course, both the pointer and the pointed-to data may be volatile: volatile unsigned char *volatile … Read more
Runtime-Evaluation An online method is to paint the complete stack with a certain value, like 0xAAAA (or 0xAA, whatever your width is). Then you can check how large the stack has maximally grown in the past by checking how much of the painting is left untouched. Have a look at this link for an explanation … Read more
Some USB hubs have the ability to turn power off to its downstream devices. “Is it possible to power up ports on a USB hub from Ubuntu?” https://askubuntu.com/questions/149242/is-it-possible-to-power-up-ports-on-a-usb-hub-from-ubuntu Which points to some c source for hub-ctrl.c See: http://www.gniibe.org/development/ac-power-control-by-USB-hub/index I tested this on Ubuntu with a Dream-Cheeky USB LED unit, and it did seem to turn … Read more
There are many many reasons you might want to use an RTOS. They are varied & the degree to which they apply to your situation is hard to say. (Note: I tend to think this way: RTOS implies hard real time which implies preemptive kernel…) Rate Monotonic Analysis (RMA) – if you want to use … Read more
Warning: the code here only showcases the storage aspect, it is a skeleton, no dynamic aspect (construction, copy, move, destruction) has been taken into account. I would suggest an approach using the C++0x new class aligned_storage, which is precisely meant for having raw storage. // header class Foo { public: private: struct Impl; Impl& impl() … Read more
The following works for me. The parameter volume is to be given in the range [0, 100]. Beware, there is no error handling! void SetAlsaMasterVolume(long volume) { long min, max; snd_mixer_t *handle; snd_mixer_selem_id_t *sid; const char *card = “default”; const char *selem_name = “Master”; snd_mixer_open(&handle, 0); snd_mixer_attach(handle, card); snd_mixer_selem_register(handle, NULL, NULL); snd_mixer_load(handle); snd_mixer_selem_id_alloca(&sid); snd_mixer_selem_id_set_index(sid, 0); … Read more
Main differences: ARM is a RISC style architecture – instructions have a regular size (32-bit for standard ARM and 16-bits for Thumb mode, though Thumb has some instructions that chew up 2 instruction ‘slots’) up through at least ARM v5 architecture (I’m not sure what v6 does), the interrupt model on ARM is vastly different … Read more
Ah, the joys of bitwise arithmetic. A side effect of many division routines is the modulus – so in few cases should division actually be faster than modulus. I’m interested to see the source you got this information from. Processors with multipliers have interesting division routines using the multiplier, but you can get from division … Read more
In the old days, that was how we tested and debugged device drivers. The very best way to debug such a system was for engineers to use the embedded system as a development system and—once adequate system maturity was reached— take away the original cross-development system! For your situation, several approaches come to mind: Add … Read more