How to get the APC220 rf module to transmit faster than 1 hz?

Using Arduino Programming Questions
#1

Hello! I have 2 apc220 wireless transceiver modules, but I can’t transmit and receive faster than 1hz without getting weird complications. The moment I transmit faster than 1hz (say 950ms interval) the packets are received in bunches every 2 or 3 seconds, and if I put the delay even shorter, the packets are received only when I turn off the transmitting Arduino (and a good bit is getting lost). It also doesn’t matter what the size of the package is, even if it’s just a 1 or 0.

edit: Here is a datasheet to the module: https://image.dfrobot.com/image/data/TEL0005/APC220_Datasheet.pdf

The apc220s are configured as followes:

Frequency = 433MHz
RF data rate = 9600 bps
Output power = 9
UART rate = 9600bps, but I will change this to 1200bps to get more range later.
Series checkout = no check

For the transmitting code, I will give a simple example code because it doesn’t matter really in what context the problem occurs:

#include <SoftwareSerial.h>

SoftwareSerial transmitter(3,4);

void setup() {
  transmitter.begin(9600);
}

void loop() {
  long time = millis();
  transmitter.println(time);
  delay(1000);   //this can't be lower, it can be higher however
}

And for the receiving code, it’s something like this: (I tried AltSoftSerial but it doesn’t seem to allow it to be faster either, but it’s basically software serial but more efficient and it only works for pin 8 and 9)

#include <AltSoftSerial.h>

AltSoftSerial receiver;

void setup() {
  Serial.begin(9600);
  receiver.begin(9600);
}

void loop() {
  if(receiver.available() > 1){
    String input = receiver.readString();
    Serial.print(input);    
}

Note that it does transmit and everything works, it just stops working on a shorter delay (even a few milliseconds shorter), and I also have the antennas connected if anyone is wondering.

Is there anyone else that has experience with this module? I would really like to know if there is a way to get it just a bit faster than 1hz, thanks in advance.

#2

Is this another UK CANSAT competition post, that is the RF module that specified in the kits ?

That device is rarely mentioned on here, it might need someone who actually has one to confirm how it works.

One thing I did spot was that the default power level is 13dBm, the limit for ISM use in the UK for the 434Mhz band would be lower, 10dBm (10mW).

#3

This frequency range is shared with a multitude of devices, even in your own neighborhood. To allow sharing, the legal limit of frequent transmissions is once per second, just what you have discovered. If you need more frequent transmissions, you need to look at 2.4 GHz devices.
Paul

#4

srnet:
Is this another UK CANSAT competition post, that is the RF module that specified in the kits ?

That device is rarely mentioned on here, it might need someone who actually has one to confirm how it works.

One thing I did spot was that the default power level is 13dBm, the limit for ISM use in the UK for the 434Mhz band would be lower, 10dBm (10mW).

Well, the Dutch competition actually, but I think Paul already has my answer.

Paul_KD7HB:
This frequency range is shared with a multitude of devices, even in your own neighborhood. To allow sharing, the legal limit of frequent transmissions is once per second, just what you have discovered. If you need more frequent transmissions, you need to look at 2.4 GHz devices.
Paul

Well, you are probably correct, that's really annoying though because I want to transmit the data in the GPS quiet time, but the interval is a bit too short if transmission time is considered. And using a timed interrupt causes GPS data loss, I may have to look at reconfiguring the GPS module then. Thanks for clarifying my problem!

#5

Paul_KD7HB:
To allow sharing, the legal limit of frequent transmissions is once per second, just what you have discovered.

If the device is used in the UK, and its the 434Mhz ISM band, then the normal duty cycle limit is 10%. There are no transmission rate limits that I am aware of.

And if the transmitted bandwidth is below 25khz, then you can transmit at 100% duty cycle.

#6

zeusbeer2:
Well, the Dutch competition actually, but I think Paul already has my answer.

Restrictions across Europe are often the same.

It would be unusual, in my experience, for a bare radio module to apply legal limits that may only apply in some parts of the World. If the module has a limit of 1 transmission a second, read the datasheet, it ought to be mentioned.

#7

srnet:
Restrictions across Europe are often the same.

It would be unusual, in my experience, for a bare radio module to apply legal limits that may only apply in some parts of the World. If the module has a limit of 1 transmission a second, read the datasheet, it ought to be mentioned.

Well, that makes sense. What doesn't make sense however is that the transmission limit is not noted anywhere in the datasheet. Would turning the module on and off with the EN pin (after sending a transmit command) work for force-sending the data? Making the same thing happen as when the Arduino is turned off and everything is received at once.

#8

zeusbeer2:
Well, that makes sense. What doesn't make sense however is that the transmission limit is not noted anywhere in the datasheet. Would turning the module on and off with the EN pin (after sending a transmit command) work for force-sending the data? Making the same thing happen as when the Arduino is turned off and everything is received at once.

Your neighbor will get quite upset with you when his weather station stops working.
Paul

#9

Paul_KD7HB:
Your neighbor will get quite upset with you when his weather station stops working.
Paul

That's a small price to pay if it works though. It won't be on 24/7, maybe half an hour max for small tests, and the launch will take place in a controlled military environment. If it works, that is.

#10

zeusbeer2:
What doesn't make sense however is that the transmission limit is not noted anywhere in the datasheet.

I guess its possible the modules have been supplied with custom firmware, in the UK they were part of a kit. If you had such a kit speak to whoever supplied it.

#11

srnet:
I guess its possible the modules have been supplied with custom firmware, in the UK they were part of a kit. If you had such a kit speak to whoever supplied it.

I will write an e-mail to the suppliers, thank you!