Hello everyone!
I'm back here with an exciting project and an exciting issue 
, after my post regarding the "pilot wire" (which works well by the way)!
First, a bit of context, as usual:
My new goal is know how much water is consumed in the house, still via HomeAssistant. The specifications I imposed to myself:
- The node will be powered on batteries. It should consume the minimum amount of power and therefore sleep as much as possible.
- I would like to send the amount of water consumed "reliably" every 5 minutes to avoid spamming the gateway and to save energy. And 5 minutes, no more (>= 5'01"), no less (<= 4'59").
Similarly to my previous project, I am not using any Arduino board. Only an ATMEGA328P using its own internal 8MHz clock.
To measure the amount of water I am using, I chose to buy a second-hand two-wires "Itron Cyble sensor", where "K=1". It is a very basic sensor which outputs a "signal equivalent to a dry contact signal (e.g. reed switch)".
More information about it can be found in its brochure: https://www.itron.com/-/media/feature/products/documents/brochure/cyble-sensor-water-brochure-english.pdf
Considerations:
To consume as less energy as possible, the circuit must be interrupt-driven. I can see two interrupts here:
-
On the water sensor side: whenever the sensor simulates a pushed button (meaning I've consumed a liter of water), this has to increment a variable. Once done, the chip should go back to sleep.
-
To measure 5 minutes: I've spent quite a bit of time searching for solutions to reliably measure 5 minutes, without using external components (an RTC for instance).
It seems I wasn't the only one to wonder how to have interrupts and a timer and I found this post for instance: https://forum.mysensors.org/topic/7263/remainder-sleep-time-upon-an-interrupt. However, I didn't like the solution given, which didn't look elegant to me...
Moreover, the sleep() function provided by the MySensors API wakes the radio up after sleeping and I don't need waking it up when I simply have to increment the "water consumed" variable!
And then, I discovered that the ATMEGA328P can run an asynchronous timer (called Timer2) and trigger interrupts on overflows / compare matches. But the really nice thing here is that this timer continues running in the power saving mode "SLEEP_MODE_PWR_SAVE", if a 32.768 kHz quartz is connected!
Where I am right now:
Right now, I have finished wiring the circuit on a breadboard and developing the code. Regarding the wiring, I have:
- An ATMEGA328P flashed with my code (with encryption enabled) and using its internal 8 MHz clock to operate.
- An RFM69W radio connected to the chip.
- A button connected to the arduino-equivalent pin #3 (pin 2 is used by the RFM69W radio, DI0), to simulate my Itron sensor.
- A 32.768 kHz quartz connected on the XTAL pins of the ATMEGA.
- A few other capacitors here and there, where they are needed.
Now, here is the code of my sketch:
// MySensors configuration
#define MY_RADIO_RFM69
#define MY_RFM69_NEW_DRIVER
#define MY_RFM69_ENABLE_ENCRYPTION
// Include the libraries
#include <avr/power.h>
#include <avr/sleep.h>
#include <MySensors.h>
// Global settings
#define CHILD_ID 0
// Global variables
volatile bool time_elapsed = true;
volatile int liters_consumed = 0;
MyMessage measure_msg(CHILD_ID, V_VOLUME);
// Interrupt triggered on Timer2 overflow
ISR(TIMER2_COMPA_vect){
// variable to count the number of overflows
static byte timer2_ovfs = 0;
// Increment the counter
timer2_ovfs++;
// Set the flag and reset the counter
if (timer2_ovfs >= 40) {
time_elapsed = true;
timer2_ovfs = 0;
}
}
void sensor_interrupt() {
liters_consumed++;
}
void presentation() {
sendSketchInfo("Compteur d'eau", "1.0");
present(CHILD_ID, S_WATER);
}
void setup() {
// Setup Timer2
ASSR = (1<<AS2); // Make Timer2 asynchronous
TCCR2A = (1<<WGM21); // CTC mode
TCCR2B = (1<<CS22)|(1<<CS21)|(1<<CS20); // Prescaler of 1024
OCR2A = 239; // Count up to 240 (zero relative!)
TIMSK2 = (1<<OCIE2A); // Enable compare match interrupt
// Setup interrupt on pin (INT1)
pinMode(3, INPUT);
attachInterrupt(digitalPinToInterrupt(3), sensor_interrupt, RISING);
// Disable unneeded peripherals
power_adc_disable(); // Analog to digital converter
power_twi_disable(); // I2C
// Set the sleep mode as "Power Save"
set_sleep_mode(SLEEP_MODE_PWR_SAVE);
// Enable interrupts
interrupts();
}
void loop() {
// The 5 minutes period has passed
if(time_elapsed) {
// Wake up the radio
transportReInitialise();
// Send the value
send(measure_msg.set(liters_consumed));
// Reset the timer
time_elapsed = false;
// Make the radio sleep
transportDisable();
}
// Go back to sleep
sleep_mode();
}
The problem:
However, there is a problem right now (otherwise, I wouldn't post in the "troubleshooting" section ).
On the gateway side, I can see that the node successfully registers and gets its ID. But for an unknown reason, after a few seconds, it keeps sending data as if time_elapsed never changed to false. And it never goes to sleep.
Here are the gateway logs after startup:
Aug 18 17:01:05 INFO Starting gateway...
Aug 18 17:01:05 INFO Protocol version - 2.3.1
Aug 18 17:01:05 DEBUG Serial port /dev/ttyMySensorsGateway (115200 baud) created
Aug 18 17:01:05 DEBUG MCO:BGN:INIT GW,CP=RPNGLS-X,REL=255,VER=2.3.1
Aug 18 17:01:05 DEBUG TSF:LRT:OK
Aug 18 17:01:05 DEBUG TSM:INIT
Aug 18 17:01:05 DEBUG TSF:WUR:MS=0
Aug 18 17:01:05 DEBUG TSM:INIT:TSP OK
Aug 18 17:01:05 DEBUG TSM:INIT:GW MODE
Aug 18 17:01:05 DEBUG TSM:READY:ID=0,PAR=0,DIS=0
Aug 18 17:01:05 DEBUG MCO:REG:NOT NEEDED
Aug 18 17:01:05 DEBUG MCO:BGN:STP
Aug 18 17:01:05 DEBUG MCO:BGN:INIT OK,TSP=1
Aug 18 17:01:05 DEBUG TSM:READY:NWD REQ
Aug 18 17:01:05 DEBUG TSF:MSG:SEND,0-0-255-255,s=255,c=3,t=20,pt=0,l=0,sg=0,ft=0,st=OK:
Aug 18 17:01:06 DEBUG TSF:MSG:READ,2-2-0,s=255,c=3,t=21,pt=1,l=1,sg=1:0
Aug 18 17:01:15 DEBUG TSF:MSG:READ,3-3-255,s=255,c=3,t=7,pt=0,l=0,sg=0:
Aug 18 17:01:15 DEBUG TSF:MSG:BC
Aug 18 17:01:15 DEBUG TSF:MSG:FPAR REQ,ID=3
Aug 18 17:01:15 DEBUG TSF:PNG:SEND,TO=0
Aug 18 17:01:15 DEBUG TSF:CKU:OK
Aug 18 17:01:15 DEBUG TSF:MSG:GWL OK
Aug 18 17:01:16 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=8,pt=1,l=1,sg=0,ft=0,st=OK:0
Aug 18 17:01:17 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=24,pt=1,l=1,sg=0:1
Aug 18 17:01:17 DEBUG TSF:MSG:PINGED,ID=3,HP=1
Aug 18 17:01:17 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=25,pt=1,l=1,sg=0,ft=0,st=OK:1
Aug 18 17:01:17 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=15,pt=6,l=2,sg=0:0100
Aug 18 17:01:18 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=15,pt=6,l=2,sg=0,ft=0,st=OK:0100
Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=0,t=17,pt=0,l=5,sg=0:2.3.1
Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=6,pt=1,l=1,sg=0:0
Aug 18 17:01:18 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=6,pt=0,l=1,sg=0,ft=0,st=OK:M
Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=11,pt=0,l=14,sg=0:Compteur d'eau
Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=12,pt=0,l=3,sg=0:1.0
Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=0,c=0,t=21,pt=0,l=0,sg=0:
Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=26,pt=1,l=1,sg=0:2
Aug 18 17:01:18 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=27,pt=1,l=1,sg=0,ft=0,st=OK:1
Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:34 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:36 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:37 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:38 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:39 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:41 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:42 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:43 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0
Aug 18 17:01:44 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:1
Aug 18 17:01:46 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:3
Aug 18 17:01:47 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:7
Aug 18 17:01:48 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:7
As you can see, a few seconds after registering, the node spams the gateway, sending the liters_consumed variable every second.
Do you guys know why? What can be wrong in this code?
Also, does the MySensor library generate other kind of interrupts?
Thanks in advance for your help!
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Appendix / bonus: how I get the 5 minutes period.
As mentioned, a 32.768 kHz quartz generates 32,768 clock cycles per second.
The clock prescaler has been set to 1024, meaning that I need 1024 clock cycles to add "1" to Timer2. This means that each second, 32 is added to timer2.
The "output compare register A" was set to 239, meaning that it will trigger an "Output Compare A interrupt" every time the counter reaches 239 (starting from 0 in CTC mode). So, such an interrupt will be triggered every 240 / 32 = 7.5s, waking up the microcontroller from sleep mode and adding 1 to the timer2_ovfs variable.
Finally, when I reach 40 output compare interrupts, I'm (supposed) to send the data to the controller. Since 7.5s * 40 = 300s = 5 minutes! 
