Teensy with 4 or 5 wireless temperature sensors

[CorBee]

This thread points to the same kind of issue : https://forum.pjrc.com/threads/46757...age-is-correct

So its a matter of defining the variables on both arduino and teensy side properly and unambiguous.

const uint16_t ID=1;
typedef struct {
uint16_t NodeId; //2 byte integer
float temperature; //4byte float

} PayloadFrame;
static PayloadFrame Out_Payload; //the variable used in sending data

Out_Payload.NodeId=ID;
Out_Payload.temperature=temperature;
radio.write( &Out_Payload, sizeof(Out_Payload) )

The float on teensy is default 32 bit it seems and the endian coding is the same as in arduino (LSB). So its my guess that this is the only change needed.

[bossredman]

Hi,

You cant have 8 digits in an unsigned int normally ... so something must have gone wrong in the code either when sending or reading.

Cor
PS just checked. The unsigned int should be 2 bytes and the float is 4 bytes on an arduino, so in total 6 bytes. But ... if you are receiving with a NON-arduino but a teensy you will need to make the type-definition of the structure more strictly.

Sorry been off line for a few days.
Thanls for that info.
Nothing is ever simple is it

[bossredman]

Will give the 'type-definition' stuff another crack in the morning.

On a side note in the mean time...
As a stop gap, I did what I refered to in a previous post -ie added 2000 to the reading of 1 sensor before TX'ing & 3000 to the other.
The idea being that I would know where the reading came from.

It worked fairly well but not as good as I'd.
So I editted my Rx sketch to only use 1 pipe for Reading ( at 1 point I had 3 running for 3 different remote sensors) to see if I could improve the Rx'ing of 1 sensor.

radio.openReadingPipe(1, addresses[1]);
//radio.openReadingPipe(2, addresses[2]);
//radio.openReadingPipe(3, addresses[3]);
radio.startListening();

I left all 3 TX'ers running though. (Note each has a unique Pipe address set for writting.
Weirdly though, I was still able to pick up readings of in the 2000 & 3000 range with the modified code.

Should that even be possible with only 1 pipe open for reading.

[bossredman]

Was just starting to believe it was time to give up on the 'typedef struct' stuff.

Just couldn't get it to work fully.

typedef struct {
uint16_t NodeId; //2 byte integer
float temperature; //4byte float

} PayloadFrame;

static PayloadFrame Out_Payload;

Implemented as suggested - but the recieved payload data only ever returned 1 of these 3 pairs of values: 0 & 0.00, 4 & 0.00, 32768 & 0.00
with

const uint16_t ID=4;

.
Ie never a valid temp reading for the float.
But occasionaly a valid for the ID.

No idea why - but I decided to add a 3rd piece of data to the payload structure.
It was a 2nd uint16_t sending its value as ID+ID

With this I now get either :
4,8, correct Temp reading
or
32768, 16792, 0.00
or
0, 16792, 0.00

[bossredman]

TBH.
I apprecaite folks are not recommending using my earlier stated method of adding order of a 1000 to the various senors to ID them.
But that does appear to work.

So wondering what I will actually benefit from perserving with the 'typedef struct'.

[CorBee]

Hi,

I cant answer that for you. But encoding data with the ID of a sensor is only going to work for a few sensors and a single dataset. If you ever plan to extend that becomes more and more difficult. But its your project !

Cor

[Pilot]

It sounds like either the data is not being copied into the struct, or the struct is different between the sender and the receiver.

When you ask the compiler to set aside some memory for a struct, that memory doesn't get blanked, so it will just be whatever random noise or previously-used data was there before.

32768 is a very curious value to just show up at random (in binary it's 1 followed by a bunch of 0s), a number that just happens to be extremely round for no apparent reason. That tells me something isn't aligned, like maybe you have a variable as int16_t in one place and uint16_t in another. Or, the memory location was previously used for something else, and data wasn't copied into it.

If you create this struct and stuff it with hard-coded test values (like ID=2, temp=15) rather than reading sensors or anything like that, can you receive it and get the same values out?

[CorBee]

Hi,

I sometimes have used the following code, where the pragma pack(1) forces the compiler into keeping the structure byte aligned

#pragma pack(1)
typedef struct newPayload {
	//8 bytes 
	uint8_t msgFormat; //#00
	uint8_t msgNodeId; //#01
	uint8_t msgType; //#02
	uint16_t data0; //#0304
	uint16_t data1; //#0506
	uint8_t checkId; //#07
} newPayload;
#pragma pack()

This is a message system for part of my setup, it sends both at the beginning and at the end of the structure the ID of the sensor. This allows easy/fast checking of the data as the beginning/ending byte need to be the same for a proper received message.

[bossredman]

Hi,

I decided to give up on the payload implementation.

I got it working without - so decided to invest the time on other aspects.
May revisit in future.
BUt thanks allfor the help.

Another question i have is with regards powering these units with batteries.

I'm using these NRF24L01+ Wireless Module with Breakout Adapter boards to mount the NRF24L01+ modules.
https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1.

They say it needs 5V ("..accepts your Arduino +5V supply ").
Im planning to use 3 x AA batteries (ie 4.5V) to power some of the MCU's that I cant locate near a mains socket to power.
(ie 1 Teensy 3.6 & several NANO's).
Will the MCU's 'step up' the supplied 4.5 to 5V, to provide the required 5v for these Breakout adapter boards.
Or do I need to use 4 xAAA (ie 6V).
Is it that simple or is 6v too much?

SOrry if this is a stupid question - just dont know enough about vraious electrical components & how they work.

[towe]

I'm using these NRF24L01+ Wireless Module with Breakout Adapter boards to mount the NRF24L01+ modules.
https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1.

They say it needs 5V ("..accepts your Arduino +5V supply ").
Im planning to use 3 x AA batteries (ie 4.5V) to power some of the MCU's that I cant locate near a mains socket to power.
(ie 1 Teensy 3.6 & several NANO's).
Will the MCU's 'step up' the supplied 4.5 to 5V, to provide the required 5v for these Breakout adapter boards.
Or do I need to use 4 xAAA (ie 6V).
Is it that simple or is 6v too much?

One of the pictures states it uses a AMS1117-3.3 voltage regulator. The datasheet of that claims a maximum 1.3 V drop out voltage, which means that your supply voltage should be at least 1.3 V + 3.3 V = 4.6 V.
That'll be tricky with 3 AA batteries.

I'd go with four such batteries in this case, which is just fine. The chip is rated for up to 15 V.
Note, however, that excess voltage will be wasted as heat by the regulator, so there's no point in going higher than you need.
Four rechargable 1.2 V AA batteries should also work reasonably well, or perhaps 2 18650 Li-Ion cells.

[BriComp]

These work really well. Here is a description/review https://www.youtube.com/watch?v=joAkJ9QA2bw
https://www.banggood.com/5pcs-ESP32-...r_warehouse=CN
I am using them on a multiple remote temperature sensing and control project using Ebyte E32 Lora Radios. Communicate via Serial Uart. Really good and easy to use.