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Hopefully you read the last article I posted about building an Arduino TNC to
perform packet email (Winlink) with my Android cellphone and Baofeng handheld
radio. If not, I recommend that you check it out so that this post will make
more sense.
After completing the hardware section of the TNC, I needed to flash the
firmware. I followed this guide:
http://www.mobilinkd.com/2014/09/11/arduino-kiss-tnc/
Which directed me to download this firmware:
https://raw.githubusercontent.com/mobilinkd/tnc1/arduino/images/mobilinkd-473-
arduino.hex
Which is part and parcel of this open source repository on Github:
https://github.com/mobilinkd/tnc1/tree/arduino
However, I had a little bit of trouble flashing my Arduino Nano, which was an
off brand variant made by Lafvin. The command you were supposed to run to flash
it was:
$ avrdude -c arduino -p m328p -P /dev/ttyUSB0 -b 57600 -U mobilinkd-473-
arduino.hex
But that didn’t work. I ended up reading about it online and needed to use this
command instead:
alaskalinuxuser@alaskalinuxuser-CF-52:~/Downloads$ avrdude -c arduino -p m328p
-P /dev/ttyUSB0 -B 10 -U mobilinkd-473-arduino.hex\n\navrdude: AVR device
initialized and ready to accept instructions\n\nReading |
Device signature = 0x1e950f (probably m328p)\navrdude: NOTE: "flash" memory
has been specified, an erase cycle will be performed\n To disable this
feature, specify the -D option.\navrdude: erasing chip\navrdude: reading input
file "mobilinkd-473-arduino.hex"\navrdude: input file mobilinkd-473-
arduino.hex auto detected as Intel Hex\navrdude: writing flash (13052 bytes):
\n\nWriting | ################################################## | 100%
2.15s\n\navrdude: 13052 bytes of flash written\navrdude: verifying flash memory
against mobilinkd-473-arduino.hex:\navrdude: load data flash data from input
file mobilinkd-473-arduino.hex:\navrdude: input file mobilinkd-473-arduino.hex
auto detected as Intel Hex\navrdude: input file mobilinkd-473-arduino.hex
contains 13052 bytes\navrdude: reading on-chip flash data:\n\nReading |
verifying ...\navrdude: 13052 bytes of flash verified\n\navrdude: safemode:
Fuses OK (E:00, H:00, L:00)\n\navrdude done. Thank
you.\n\nalaskalinuxuser@alaskalinuxuser-CF-52:~/Downloads$
I like to reference where I learned that, but I can’t find the article I read
anymore that originally brought me to that conclusion. Either way, that command
works for me with the “-B 10” option instead of specifying a baud rate.
Using an OTG cable, I connected my newly flashed TNC to my Android phone. I
already had WoAD installed, an app that allows you to send and receive Winlink
email, and even though the app was closed, it immediately detected that I had
plugged in the TNC, prompting me to open WoAD.
Once WoAD was open, I clicked on the menu option, selected sessions, and
clicked the “Add” button to create a new session.
Name: ArduinoTNC
Protocol: Packet
Type: Outgoing
Auto-connect: None
Notes: (I left blank)
Settings ->
Destination address: KL7EDK-10 ( a local station I connect with )
TNC type: KISS
TNC Settings ->
Over-the-air data rate (baud) : 1200
Tx delay (ms) : 500
Maximum packet length : 128
Max outstanding frames : 4
Frack time (sec) : 4
Persistence : 64
Slot time (ms) : 300
Max retries : 10
Tx tail (ms) : 20
TNC configuration ->
Connection type: USB
Connection configuration: (When you click on this, choose your TNC USB port, it
only shows one for me, since only one USB device is connected.)
Device manufacturer: Generic
Kiss Port number: 0
And that’s it! I will note that in the previous post I talked about my big slow
relay causing a problem. Typically, your Tx delay is shorter, like 300 ms, but
with that relay being extra slow, I had to increase the Tx delay to 500 ms.
Essentially, this means that it keys the push to talk switch, then waits 500
milliseconds before transmitting the data. This ensures that the relay had time
to switch before sending the data.
That said and done, I was able to connect to a local Winlink gateway station
and, as you can see in the pics, send and receive email. I did notice however,
that with larger emails, the TNC would stop sending/receiving. What I don’t
know for sure, is if it is my Baofeng radio or the TNC that causes the failure.
You see, my Baofeng battery failed, so I “replaced” it with a 9 volt battery,
as you can see and read about in my previous posts. However, a drawback to the
9 volt battery is transmitting power is severely limited compared to a standard
battery. So I don’t know if the longer transmit times of bigger emails starts
to “hammer” the battery until it doesn’t work (plausible, since the battery
meter drops to 0 bars when transmitting), or if the TNC gets choked up on
larger buffered information.
One way to test would be to get really close to the gateway station, so that if
my transmit power is limited, it will still be enough to key the gateway. Or,
perhaps I can borrow someone else’s handheld radio to test with. I could also
hot wire a plug for my HTX-212 transceiver in the truck, it has 45 watts of
output power, so I’m pretty sure that would rule out anything related to power
of transmission. Some more testing is in the foreseeable future.
Either way, it’s been a fun project!
Linux – keep it simple.