Changing behaviour of TX pin

[Samúel Úlfr Þór Hjaltalín Guðjónsson]

Hi all.

Not sure this group is still active, but I thought I might give it a shot.

So I've been building á digipeater using extdigi and NRX1 and HX1 modules from Radiometrix, and the HX1 expects active Hi signal from the Arduino, but I also had to drive a relay for tx/rx switching so I decided to go with a PNP transistor instead, and trying to minimize how many components I needed I thought I could easily just change the behaviour of pin 11 (arduino) from active hi to active low. 

However going through the code I cannot seem to find the piece of code that activates digital pin 11 on the ATmega328 (which is hardware pin 17). I realize that this could easily be done on a hardware level but I've already had the PCB printed before I realized how difficult this would be. 

If anyone has any info that could point me into the correct direction as in which file this part might lie in that'd be greatly appreciated.

P.s. for those interested the final hardware design will be open source after I finish the project.

Best regards,

Samuel Hjaltalin

TF3SUT

[Gary Barker]

Samuel: Did you ever find the code to change this? I notice in the trackuino program they have a file radio_hx1.cpp to control the ptt function but it doesn't exist here.

73,

de Gary

VE6UQ

[Alejandro Santos]

Hi all,
I haven't worked in this project for a long time.
The original BeRTOS website no longer exists, but you can take a look
at the schematic here:
http://web.archive.org/web/20150216025741/http://www.bertos.org/use/examples-projects/arduino-aprs/
Looks like it's Pin 4. I've been just trying to read the source code
to see how true that is with extdigi with no luck.
Best regards,
Alejandro LU4EXT

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Alejandro Santos

[Samúel Þór Hjaltalín Guðjónsson]

Hi
No I didn’t find out, but ended up changing the circuit that I was designing.

Btw, I finished the digipeater that I was building and the schematics and eagle files are available on my website
https://ulfraf.space/APRS-TF0-digi.tar.gz

In the software I’ve been trying to figure out two things
1) For some reason the beacon string adds a 0x00 (null terminator in C) at the end of the string, and I haven’t been able to figure out why. (I’m more of a hardware guy than a software guy though)
2) I want to add telemetry to the code but I haven’t figure that out yet.


73 de TF2SUT
Samuel Hjaltalin

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[Gary Barker]

Samuel: Thanks for sharing your design. I am using a NiceRF SA828 transceiver which requires a low signal for PTT. I tried a quick hardware fix by using a 2N7000 for an inverter and it worked for the PTT function but for some strange reason it seems to act as a low pass filter since the modulation of the transmitter output sounds like a CTCSS tone.

On the software end of things, I see that in the trackuino program they use the pinMode and pin_write commands to configure the pins but these do not turn up in a search of the bertos software here, so I don't know how they configure them. I thought it would have been in the documentation since there are other radios that use a low state to trigger PTT.

For telemetry on another project I have used an Arduino Nano to send temperature readings from an OSEPP HUMI-01 to a Raspberry Pi on the I2C bus which then uses the Direwolf program to beacon out these values on the radio.

73 de VE6UQ,

Gary

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> Alejandro Santos
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[Samúel Þór Hjaltalín Guðjónsson]

Hi Gary

I’m guessing there’s crosstalk going on since PTT is at pin 20, TXD is at pin 19, and RXD is at pin 18 (unless I’m misunderstanding something).

Perhaps adding a 0.1nF capacitor on the PTT line could couple the noise out? 

Do you have a schematic to share?

73 de TF2SUT

Samúel Hjaltalín

On 16 Jul 2020, at 15:27, Gary Barker <gbar...@gmail.com> wrote:

NiceRF SA828

[Gary Barker]

Samuel: Sorry for the delay, I was out of the email service area for a few days. My schematic is attached. At this point I am just testing the transmitter modulation via beacons so I wouldn't think that crosstalk would be a factor.

P.S. I notice in section 6 of your manual (Programming of the device) that some portions have not been translated to English.

73, 

de VE6UQ

Gary