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ykaw / PiCW

A morse code keyer running on Raspberry Pi
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question about: docs/schematic.txt #3

Open jacksnodgrass opened 8 months ago

jacksnodgrass commented 8 months ago

In the docs/schematic.txt file you say:

(future plan: TX control)

for GPIO22

does that mean that the TX function of the code..... TX of rig connected to GPIO22 won't work if I connect my transmitter to that pin or what exactly.... what is 'future' about that pin?

ykaw commented 8 months ago

Since the GPIO only outputs a DC voltage, simply connecting it directly to the TX keying circuit will not work (in addition, the direct connection may cause the RaspPi to fail.) To control the TX, a switching circuit using a transistor or a photo-MOS switch, etc. must be inserted. I will update the schematic in due course.

jacksnodgrass commented 8 months ago

Ok. Thanks for the explanation. A mechanical relay or SSR could also be used... probably..... I use one of those with a different Pi in my garage to control my driveway gate. I'll see about using that to control the TX on the rig. Will let you know how it goes. Thanks again.

jacksnodgrass commented 8 months ago

Had another question(s) about the schematic.txt file...

Is the 1k ohm resistor and the 10uF cap on the pwm output to the speaker really needed.... i.e. what is their purpose. For 'testing' I just hooked up GPIO18 directly to my Kenwood SP-930 speaker and I heard tone. Sounded fine to me.... are those extra components really that important?

AND... you have 3 pins listed on the Side Tone Out... but I guess you just use 2.... R and E (common ) What are 'L', 'R', and 'E' supposed to mean.... of you're only using 2 pins for speaker... why list 3... that confuses me. ( I confuse easily )

ykaw commented 8 months ago

The resistor may serve as a protective measure by limiting overcurrent, mitigating the impact of excessive current that the PWM signal might induce. And capacitors contributes to cutting the DC component, ensuring that only the desired AC component of the PWM signal passes through. This is particularly relevant for applications where removing the DC component is essential to prevent unwanted energy supply to devices, enhancing efficiency and stability.

And its output is intended to be output from a stereophone jack, so there are left(L) and right(R) terminals. If you only need to hear out of one ear or use a mono phone jack, the output jacks are of course a pair.