When input pullup is NOT used, a floating connection is low (or presumably low).

As I stated when I put it there, it came from the Arduino docs.

Vince.



On 10/01/2017 07:38 PM, Allard PE1NWL wrote:

On Sun, Oct 1, 2017 at 04:01 pm, Vince Vielhaber wrote:

On the digital pins:

There are 20K pullup resistors built into the Atmega chip that can
be accessed from software. These built-in pullup resistors are
accessed by setting the pinMode() as INPUT_PULLUP. This effectively
inverts the behavior of the INPUT mode, where HIGH means the sensor
is off, and LOW means the sensor is on.

This is absolutely INCORRECT.
pinMode(xx, INPUT) and pinMode(xx, INPUT_PULLUP) only enable/disable the
internal pull up resistors.
They DON'T invert the behaviour of the input!

73 Allard PE1NWL

On Sun, Oct 1, 2017 at 04:01 pm, Vince Vielhaber wrote:

On the digital pins:

There are 20K pullup resistors built into the Atmega chip that can
be accessed from software. These built-in pullup resistors are
accessed by setting the pinMode() as INPUT_PULLUP. This effectively
inverts the behavior of the INPUT mode, where HIGH means the sensor
is off, and LOW means the sensor is on.

This is absolutely INCORRECT.
pinMode(xx, INPUT) and pinMode(xx, INPUT_PULLUP) only enable/disable the
internal pull up resistors.
They DON'T invert the behaviour of the input!

73 Allard PE1NWL

Or even better:

//configure the PTT SENSE to use the internal pull-up
pinMode(PTT_SENSE, INPUT_PULLUP);
// check if PTT sense line is installed
PTTsense_installed = !digitalRead(PTT_SENSE);
pinMode(PTT_SENSE, INPUT); //disable the internal pull-up

saves 6 bytes.

Unplug the vol control from the board and see if touching the pin that would connect to the wiper gives you noise.? That isolates the preamp from the circuit.? If you get the noise you used to get, look at the preamp stage.? If not, look at the LM386.

Do you have a scope?

Vince.



On 10/01/2017 06:02 PM, Ken Macy wrote:

On Sun, Oct 1, 2017 at 12:00 pm, Ashhar Farhan wrote:

??? audio preamp might be busted. the LM386 seems to be working (from
??? the test that you performed). check the voltages around the audio
??? preamp's base and collector.
??? if the LM386 gives you noise, does the volume control give you noise
??? too? trace the connectivity from pin 3 of the LM386 to the volume
??? control's middle lug. if the noise ensues when you touch a wire to
??? the middle lug of the volume control, then move to the upper lug
??? (not the one connected to the ground), if that works, then, check at
??? the collector of the audio preamp. essentially, you hve to get to
??? the point beyond with the audio doesn't pick up and you have located
??? the trouble.


Farhan, thanks for replying, thanks for your patience.?? Here are the
responses to your thoughts:

audio preamp might be busted.
/*Uh-Oh!? Q16?
*/
the LM386 seems to be working (from the test that you performed). check
the voltages around the audio preamp's base and collector.
/*base: 0.7v?? collector: 1.6v?? emitter: 0v
*/
if the LM386 gives you noise,
/*just touching pin3 no longer gives noise, injecting a 1KHz audio tone
0dB there does appear out the speaker, the 386 is amplifying
*/
does the volume control give you noise too?
*/just touching middle lug no longer gives noise, injecting a 1KHz audio
tone 0dB there does appear out the speaker/*/, the 386 is amplifying/*/
/*
trace the connectivity from pin 3 of the LM386 to the volume control's
middle lug.
/*there is direct connection
*/
if the noise ensues when you touch a wire to the middle lug of the
volume control,
/*there is no noise touching wire here nor anywhere else
*/
then move to the upper lug (not the one connected to the ground),
/*there is no noise touching wire here nor anywhere else
*/
if that works, then, check at the collector of the audio preamp.
/*no noise there either
*/
essentially, you hve to get to the point beyond with the audio doesn't
pick up and you have located the trouble.
/*I agree, but there is no audio anywhere apparently*/

Given all this, should I attempt to replace Q16, audio pre-amp?
?Watching your troubleshooting video, I ran into immediate fail starting
with touching the back of the BNC antenna connector - silence! Then
silence at each and every point that you highlight.? But yet the
transmitter works!

-KG6PO

Jerry,
now I think of it- I have a much better idea:

at startup, initially enable the pullup at A0 and check if the PTTsense is
installed.
Then disable the pullup, like so:

//configure the PTT SENSE to use the internal pull-up
pinMode(PTT_SENSE, INPUT_PULLUP);
// check if PTT sense line is installed
if (!digitalRead(PTT_SENSE))
PTTsense_installed = true; //yes it's installed
else
PTTsense_installed = false; //no it's not installed
pinMode(PTT_SENSE, INPUT); //disable the internal pull-up

This way we get a nice zero volts on A0 during RX.

73 Allard PE1NWL

On Sun, October 1, 2017 23:46, Allard PE1NWL wrote:

Jerry,

Correct, we need the pullup on A0 for reasons of backward compatibility.
At startup the firmware detects whether or not the PTTsense line is
installed. When the PTTsense is NOT installed, input A0 will be open.
Without a pullup the digital level will be undefined so we won't be able
to reliably detect this condition.

With the pullup resistor enabled, and a 10K resistor in the PTTsense
line,
we typically get 1.25V on A0 during RX, which is well below the
threshold.
You could use a smaller resistor value but it shouldn't be necessary.

BTW, the 1.25V suggests that the internal pullup resistors are about
30K,
which is smaller than I expected (I've always thought they were at least
50K).

73 Allard PE1NWL

On Sun, October 1, 2017 20:01, Jerry Gaffke via Groups.Io wrote:

Allard,

You are writing your firmware in such a way that users need not apply
all
mods.
That might require a pullup or pulldown on A0, in which case it's best
to
ignore my previous post.
If thresholds at A0 become an issue, perhaps the recommended resistor
at
A0 could be reduced from 10k,
Perhaps as low as 1k?

Measurements are probably the best source of information here.
However, from the datasheet:

Figures 33.25 and 33.26 on pages 391 and 392 of ??
??
(

)
show the input threshold with Vcc at 5v to be somewhere between 2.1 and
2.7 volts for a digital input on the ATmega328p

Figure 33.17 on page 387 shows pullup current from a pin at 1.3v to be
around 100uA, so (5-1.3)/0.1mA = 37k
for the typical effective pullup resistance for an ATmega328p digital
input with Vcc at 5v.

Jerry

On Sun, Oct 1, 2017 at 10:39 am, Jerry Gaffke wrote:

Allard,

What you have works well enough.
But on the next rev of firmware, you might remove the pullup from A0.
(As you are likely already planning to do.)

On Sun, Oct 1, 2017 at 12:00 pm, Ashhar Farhan wrote:

audio preamp might be busted. the LM386 seems to be working (from
the test that you performed). check the voltages around the audio
preamp's base and collector.
if the LM386 gives you noise, does the volume control give you noise
too? trace the connectivity from pin 3 of the LM386 to the volume
control's middle lug. if the noise ensues when you touch a wire to
the middle lug of the volume control, then move to the upper lug
(not the one connected to the ground), if that works, then, check at
the collector of the audio preamp. essentially, you hve to get to
the point beyond with the audio doesn't pick up and you have located
the trouble.


Farhan, thanks for replying, thanks for your patience. Here are the
responses to your thoughts:

audio preamp might be busted.
/*Uh-Oh! Q16?
*/
the LM386 seems to be working (from the test that you performed). check
the voltages around the audio preamp's base and collector.
/*base: 0.7v collector: 1.6v emitter: 0v
*/
if the LM386 gives you noise,
/*just touching pin3 no longer gives noise, injecting a 1KHz audio tone
0dB there does appear out the speaker, the 386 is amplifying
*/
does the volume control give you noise too?
*/just touching middle lug no longer gives noise, injecting a 1KHz audio
tone 0dB there does appear out the speaker/*/, the 386 is amplifying/*/
/*
trace the connectivity from pin 3 of the LM386 to the volume control's
middle lug.
/*there is direct connection
*/
if the noise ensues when you touch a wire to the middle lug of the
volume control,
/*there is no noise touching wire here nor anywhere else
*/
then move to the upper lug (not the one connected to the ground),
/*there is no noise touching wire here nor anywhere else
*/
if that works, then, check at the collector of the audio preamp.
/*no noise there either
*/
essentially, you hve to get to the point beyond with the audio doesn't
pick up and you have located the trouble.
/*I agree, but there is no audio anywhere apparently*/

Given all this, should I attempt to replace Q16, audio pre-amp?
Watching your troubleshooting video, I ran into immediate fail starting
with touching the back of the BNC antenna connector - silence! Then
silence at each and every point that you highlight. But yet the
transmitter works!

-KG6PO

Jerry,

Correct, we need the pullup on A0 for reasons of backward compatibility.
At startup the firmware detects whether or not the PTTsense line is
installed. When the PTTsense is NOT installed, input A0 will be open.
Without a pullup the digital level will be undefined so we won't be able
to reliably detect this condition.

With the pullup resistor enabled, and a 10K resistor in the PTTsense line,
we typically get 1.25V on A0 during RX, which is well below the threshold.
You could use a smaller resistor value but it shouldn't be necessary.

BTW, the 1.25V suggests that the internal pullup resistors are about 30K,
which is smaller than I expected (I've always thought they were at least
50K).

73 Allard PE1NWL

On Sun, October 1, 2017 20:01, Jerry Gaffke via Groups.Io wrote:

Allard,

You are writing your firmware in such a way that users need not apply
all
mods.
That might require a pullup or pulldown on A0, in which case it's best
to
ignore my previous post.
If thresholds at A0 become an issue, perhaps the recommended resistor at
A0 could be reduced from 10k,
Perhaps as low as 1k?

Measurements are probably the best source of information here.
However, from the datasheet:

Figures 33.25 and 33.26 on pages 391 and 392 of ??
??
(

)
show the input threshold with Vcc at 5v to be somewhere between 2.1 and
2.7 volts for a digital input on the ATmega328p

Figure 33.17 on page 387 shows pullup current from a pin at 1.3v to be
around 100uA, so (5-1.3)/0.1mA = 37k
for the typical effective pullup resistance for an ATmega328p digital
input with Vcc at 5v.

Jerry

On Sun, Oct 1, 2017 at 10:39 am, Jerry Gaffke wrote:

Allard,

What you have works well enough.
But on the next rev of firmware, you might remove the pullup from A0.
(As you are likely already planning to do.)

Some do take longer than others to arrive:
/g/BITX20/message/22442

This tidbit from the first post in that thread might be informative:
"I had an email exchange with hfsignals at gmail dot com. They said if
deemed not deliverable, it should come back to them. And that the
package labels are directly printed from the PayPal system and covered
with clear protective tape. I've verified that the address is correct
in the email I got from PayPal."

IndiaPost tracking numbers (you may have one from HFSigs or PayPal) can
be tracked by a USPS postal clerk if you ask nicely and they aren't
swamped with work. Maybe ask at a small rural post office sometime you
have a chance. The publicly accessable tracking system for IndiaPost
knows nothing once the package leaves India.

Jerry

On Sun, Oct 1, 2017 at 02:42 pm, <paul@...> wrote:

I'm still waiting for my BitX kit (I fear it may have gone missing)

While reading this thread, I am sure that many builders have wired their
BITX-40's for dual voltages. If you have, I would like to see a posting
here on just how you accomplished it. This would save me a little work
on trying to figure it out, hi hi. I am thinking of dual position
switch, (I would mount it on the rear of the chassis) that would have
the entire radio to operate on 12vdc, with the second position, putting
24vdc on PA only. Please, your schematic here. 73, de KO8S, Karl


On Sunday, October 1, 2017 3:23 PM, Keith VE7GDH <ve7gdh@...> wrote:


Paul (call sign?) wrote...

confused on the e DC power connection instructions...

The post at /g/BITX20/message/23973
that Jerry pointed out pretty much says it all.

Keep in mind that there are two places on the main
circuit board that need to get power. The Raduino
also needs power. The power connection at the back
right of the main board (if you have the PA at the
back) is power to everything else on the main board.
The power connection over near the IRF510 PA is for
the final and nothing else. This is so you can
optionally run the PA at a higher voltage... with a
larger heat sink. If you are going to run everything
on 12V, just connect the three places together
wherever you switch the power on and off and of
course tie all of the grounds together too, avoiding
ground loops.

--
73 Keith VE7GDH

Check my photo album at the site, then.

Jack, W8TEE

---

From: "dm5tu@..." <dm5tu@...>
To: [email protected]
Sent: Sunday, October 1, 2017 1:59 PM
Subject: Re: [BITX20] W8TEE pending software release and port(?) #w8tee

Hi Jack,

sorry but my feedback is the same... no ?inline picture on the side. I am even logged in.

TNT fer all . sTef DM5TU es 72/3`s