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by bns23
Sun Aug 24, 2014 9:11 pm
Forum: C/C++
Topic: Is this an array?
Replies: 2
Views: 605

Re: Is this an array?

Should be an array of function pointers...
by bns23
Fri Aug 08, 2014 8:02 am
Forum: Bare metal, Assembly language
Topic: FIFO to solve I2S jitter. Any solution?
Replies: 18
Views: 10231

Re: FIFO to solve I2S jitter. Any solution?

From the product description : ... On top of that the Isolation module has an embedded isolated fixed master clock to give the user the ability to use it with any DAC that requires a master clock which the Raspberry PI is missing. Well, for me, this doesn't sound like the clocks/signals are all re-...
by bns23
Fri Aug 08, 2014 7:07 am
Forum: C/C++
Topic: float values to LCD
Replies: 6
Views: 1455

Re: float values to LCD

example_WriteText(temp); This looks suspicious, too. Why do you first convert the float value to a string using sprintf, and then pass the pointer to the float value to the function? I think you have to think over what you are doing here - which functions take which types of variables. Even, it loo...
by bns23
Fri Aug 08, 2014 6:59 am
Forum: C/C++
Topic: float values to LCD
Replies: 6
Views: 1455

Re: float values to LCD

unsigned char buf = malloc(sizeof buf); This is wrong! Don't you get a compiler warning because of this line? You should read a bit about pointers and memory allocation in C... :D I think you want something like this: #define BUFLEN 80 char* buf = malloc(BUFLEN); and at the end of course: free(buf)
by bns23
Thu Aug 07, 2014 9:12 pm
Forum: C/C++
Topic: Low Level (FAST) GPIO Access
Replies: 53
Views: 14858

Re: Low Level (FAST) GPIO Access

The Raspberry Pi SPI peripheral (/dev/spidev0.0 and /dev/spidev0.1) is solely a master device. There is no mechanism for it to respond to an interrupt to get a sample, it instigates all transfers. From Linux userland there is no way to trigger a SPI transfer using the SPI peripheral at a guaranteed...
by bns23
Thu Aug 07, 2014 8:32 pm
Forum: C/C++
Topic: Low Level (FAST) GPIO Access
Replies: 53
Views: 14858

Re: Low Level (FAST) GPIO Access

...which you won't be able to achieve by using the SPI peripheral. You'll need to bit bang SPI and use DMA timing. Unless, of course, the data is sampled remotely with precise timing, buffered, and then fed into the Pi's SPI peripheral. But in that case why not just buffer the data and use any old ...
by bns23
Thu Aug 07, 2014 6:12 pm
Forum: C/C++
Topic: Low Level (FAST) GPIO Access
Replies: 53
Views: 14858

Re: Low Level (FAST) GPIO Access

In general, using the SPI will cause much less CPU load then driving the GPIOs by software, because the peripheral will take care of driving the clock lines, reading in / writing out every bit etc. For reading in, you just configure the SPI (clocking speed, number of bits to read etc.) and start it....
by bns23
Thu Aug 07, 2014 5:40 pm
Forum: Bare metal, Assembly language
Topic: FIFO to solve I2S jitter. Any solution?
Replies: 18
Views: 10231

Re: FIFO to solve I2S jitter. Any solution?

Hi, it's very fine to use the RPi for this - I'm thinking of doing something similar. My sarcastic statement comes from a quick calculation of the BOM of this device - I expect that even if you buy it in low quantities it will not cost more than 20-25 EUR (including PCB). Raspberry Pi is a community...
by bns23
Thu Aug 07, 2014 3:52 pm
Forum: Bare metal, Assembly language
Topic: FIFO to solve I2S jitter. Any solution?
Replies: 18
Views: 10231

Re: FIFO to solve I2S jitter. Any solution?

if you are willing to pay $125 for insulation and reclocking on a 35$ RPi, I recommend you also buy my super-precise "Golden Bamboo Caps", hand-crafted by 80 years old Burmese virigins, that will drive the RPi power supply to another level.I will start to sell them soon... Serious: What kind of supe...
by bns23
Thu Aug 07, 2014 1:42 pm
Forum: C/C++
Topic: Low Level (FAST) GPIO Access
Replies: 53
Views: 14858

Re: Low Level (FAST) GPIO Access

Hi edbird, maybe I did not understand what you are trying to achive -- this is the reason why I asked for details. My assumption was that you try to interface an audio ADC by using GPIOs, and you think you can achieve this if you are just able to drive the GPIOs fast enough. But I'm pretty sure that...
by bns23
Thu Aug 07, 2014 12:43 pm
Forum: Bare metal, Assembly language
Topic: FIFO to solve I2S jitter. Any solution?
Replies: 18
Views: 10231

Re: FIFO to solve I2S jitter. Any solution?

Ah great, didn't see this. Thanks for the info.
by bns23
Thu Aug 07, 2014 12:14 pm
Forum: Bare metal, Assembly language
Topic: FIFO to solve I2S jitter. Any solution?
Replies: 18
Views: 10231

Re: FIFO to solve I2S jitter. Any solution?

Hi,

are you talking about I2S over USB here? Because all RPi version before B+ haven't routed the PCM_FS signal to any header (if this site is right: http://elinux.org/RPi_BCM2835_GPIOs).
So you are not able to interface via I2S to any DAC directly on all RPis Rev. A and B, or do I miss something?
by bns23
Thu Aug 07, 2014 10:54 am
Forum: C/C++
Topic: Low Level (FAST) GPIO Access
Replies: 53
Views: 14858

Re: Low Level (FAST) GPIO Access

Hi, I guess the ADC has an I2S interface (or similar) -- all audio DACs and ADC I'm aware of have this kind of interface. http://en.wikipedia.org/wiki/I%C2%B2S If so, the solution to interfacing with GPIO is simple: forget it. You need a compatible interface (peripheral) that handles the signal for ...
by bns23
Thu Aug 07, 2014 8:25 am
Forum: C/C++
Topic: Low Level (FAST) GPIO Access
Replies: 53
Views: 14858

Re: Low Level (FAST) GPIO Access

Hi ebird,

you haven't clearly stated what kind of device you want to interface with, but because you talk about 44100 Hz sampling rate I assume you try to interface with some audio ADC or DAC. Is this right?

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