Re: Is software demodulation of 455 kHz possible on a Raspberry Pi 3

[Bengt M. <bu...@be...>]

On 12/02/16 17:34, Sof...@qu... wrote:
...
>>> The ultimate goal is to blast (not to receive).
>>
>> This should be straightforward, or is there a problem?
> Well, it does not work. Either the codes are wrong or the RPi is not fast enough for software pwm at 455 kHz or I made some other error. Thus, I ike to first test the codes.

IMHO, using a general-purpose Linux system for generating software PWM 
is like using a microscope to hammer in nails: A microscope does not 
make a very good hammer, and you might damage the delicate instrument; 
BUT --- you may get the work done, if the task was not too challenging :-).

One thing to try on the RPi is hardware PWM (cf. 
https://github.com/bengtmartensson/lirc_rpi/issues/1). But it still does 
not take all the timings load from the main CPU.

>>> Nevertheless, to test, I like to confirm the derived codes by receiving them with mode2. The only demodulating IR receiver I could purchase is a no name receiver shipped from China; claimed to be an original TSOP9000 which appears to be not correct.
>>
>> ??? Possibly you mean TSOP7000? There is a number of offers on EBay and
>> Aliexpress.
> It is(or should be) a TSOP7000, apologies. The outer shape/size is slightly different than published for a real, orig i na l TSOP7000 and it fires constantly even in the absence of an IR remote signal. I assume electrical noise or visible light.

For power supply disturbances, the standard method is to connect a small 
capacitator between power and ground immediately at the sensor;  it is 
even in the "Application circuit" on page 1 on the data sheet. (It also 
contains a 1k pullup on the output; might be worth a try.) Try both 3.3V 
and 5V as supply, may make a difference.

Ambient light can be turned off, at least for testing.

Greetz,

Bengt