Slim Node Si7021 sensor example

[m26872]

@rsachoc I'm sorry, I know I need to update those old pictures.

[rsachoc]

@m26872 no problem, not your fault at all, mine for being a newbie. So much so that my first attempt resulted in me soldering the capacitor to the wrong hole, so I've had to abandon my first attempt. You live, you learn, next time I'll double check.

[m26872]

@rsachoc Yes. Double check polarity of the 4.7uF cap.

[rsachoc]

Hi all, again.

I have now successfully built (I think) the slim node, but without the 7021 temp sensor. Because this is the most expensive part of the device and because I find desoldering a challenge, but mainly because I'm waiting for it to arrive from China, can I try and upload the bootloader and sketch without the sensor attached?

If so, I had a couple questions from reading through this thread and the slim node thread. Firstly, uploading the bootloader, can this be done with the FTDI adaptor or do I need to follow the bit described in the slim node thread and attempt it using AVR studio? Secondly, once that is done, is it just a matter of uploading the sketch provided above?

Also, I wanted to confirm a few things on attaching the si7021 temp sensor. From what I can see, SOA (SDA) on the si7021 goes to A4 and SCL goes to A5. Also, GND goes to GND on the board (rightmost set on pins bottom right when FTDI is at the top) and VIN goes to VCC (just next to GND on the board)?

Thanks in advance.

[m26872]

@rsachoc said:

can I try and upload the bootloader and sketch without the sensor attached?

Yes, you should be able to get far without the sensor. Send something over MySensors net and view debug prints. Or make some simple sensor like a reed switch.

uploading the bootloader, can this be done with the FTDI adaptor or do I need to follow the bit described in the slim node thread and attempt it using AVR studio?

Yes, Avr Studio or Uno as ISP.

Secondly, once that is done, is it just a matter of uploading the sketch provided above?

Yes, but if you don't connect a Si7021 I would go for some other simple test sketch to avoid any Si7021 library startup issues.

Also, I wanted to confirm a few things on attaching the si7021 temp sensor. From what I can see, SOA (SDA) on the si7021 goes to A4 and SCL goes to A5. Also, GND goes to GND on the board (rightmost set on pins bottom right when FTDI is at the top) and VIN goes to VCC (just next to GND on the board)?

Yes.

[rsachoc]

Folks, a word of caution, for people that are attempting this for the first time, please burn the bootloader before you solder everything, as silly me, I built the entire thing (without the si7021) and now I'll need to bin it because the ATMega is soldered to the board and I've no way to load the bootloader soldered to the board!

Ah, the life of a newbie :grin:

I think what I'll do is once I've actually got a working board, I'll do a newbie writeup so that people don't make the same mistakes as me.

[mfalkvidd]

First Attempt In Learning :-) A writeup would be awesome.

[m26872]

@rsachoc Why don't you just solder some wires to pins you need ? The "in cicuit serial programming" concept would let you do it with almost anything attached.

[rsachoc]

@m26872 said:

@rsachoc Why don't you just solder some wires to pins you need ? The "in cicuit serial programming" concept would let you do it with almost anything attached.

I might as well attempt that! I'm waiting for a breadboard, so I'll try and attempt it when that arrives.

[rsachoc]

Some of my tips (noob alert) that I've gathered in my travels so far for this temp Slim node

1. Burn the bootloader onto the ATMega328 first! (here is a guide for Arduino as ISP)
2. Check the capacitor polarity before you solder it (the 4.7uF electrolytic capacitor, the others don't matter)
3. I prefer using strips for the Atmega (see here) as you'll have more clearance for the capacitors which sit underneath (there is a caveat to this however, in that if you're not sure if you've got/burnt a bootloader onto the ATMega, using strips there is no going back, whereas with the chip socket, you can remove the ATMega). Update I think, for me anyway, if you're confident that the ATMega has been bootloaded successfully, I still prefer strips, however if you're unsure what you can do is use the socket and just sit it higher in it's position to get a decent clearance.
4. The bill of materials (BOM) is here and also helps with figuring out which pieces go where
5. Solder the capacitors, wires for Si7021 (with si7021 attached) and FTDI pins to the board first, then the strips + AtMega328p (see below), then the NRF last to the board. I found that the FTDI pins facing straight up were best for the box I was going to put it in
6. Solder the strips to the ATMega first, then to the board
7. Check the size of the box/fitting you are going to mount this in before you do all the above!
8. Check that you are putting the ATMega chip the right way on the board, the notch should be facing the pins for the FTDI.
9. Check continuity of the pins from the ATMega to the board pins underneath, I found the ATMega to strips were the most difficult to solder, and after I tested continuity I found a single pin which didn't have connection, so I added some more solder to this pin.
10. Don't forget the resistor at R1 (I soldered this to the underside of the board, less by choice and more by the fact that I forgot about it, but I guess the preference would be the same side as the capacitors)
11. I strongly advise buying the 3.3v ready si7021 temp sensor (here) as the modification to the 5v version is quite difficult for a newbie (the components are quite small) and you'll probably mess it up like I did.

General soldering tips
12) Practice soldering first, some of the joins are a little challenging and it took me a few attempts to get the hang of it
13) Get a decent size tip, my first was a bit large

[GertSanders]

@rsachoc As a great man once said: "most bananas grow bent, and yet everyone loves them. There is nothing strange about the diversity of routes to success"

[rsachoc]

Thanks all, I'm sure I will be adding to it, as I'm now trying to compile and upload the sketch. However, I'm getting the following error:

   #error No forward link or gateway feature activated. This means nowhere to send messages! Pretty pointless.

    ^

exit status 1
Error compiling.

I'm using the W5100 MQTT gateway sketch (which I believe is on the development branch), so I'm not sure if that's what's causing the error? I've tried deleting the Arduino IDE, the mysensors development branch from my PC, and reinstalling and redownloading the mysensors dev branch, but the same thing happens?

[rsachoc]

OK, so it seems that it was because I was using the dev branch that I'm getting that error. I switched over to stable and the sketch compiles, although I do get a warning.

WARNING: Category '' in library UIPEthernet is not valid. Setting to 'Uncategorized'

But I also can't upload the sketch above:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x18

I noted above that something needed to be changed in terms of the baud rate, mine is set at 115200 in myconfig.h and I can't seem to find a reference in mysensor.h

[m26872]

@rsachoc I sorry, but there seems to be an error in the sketch in the first post. Baud rate should be 9600 everywhere if you use the common Slim Node fuses and bootloader. Upload (board.txt), MyConfig.h (not MySensor.h since v1.5), Debug-prints and Arduino IDE serial monitor.

[rsachoc]

Thanks, I've updated the sketch that I downloaded, also myconfig.h so that should be good. What do I need to select in the Arduino IDE for board type? I searched in the slim node thread and didn't see a reference to any changes?

[m26872]

@rsachoc No changes. It is that boards.txt entry you should use.

[rsachoc]

Hmmm ok, that's what I thought...still no luck, I've modified the boards.txt with the text from the slim node thread, and now it still has the same error message.

To confirm, my FTDI adaptor is attached to the board pins as follows:

FTDI <-> board
GND <-> first pin (i.e bottom left of board when looking at board laying long side horizontal and NRF radio on the other side)
CTS <-> board marked GND
PWR <-> board marked VCC
TXO <-> next up i.e. 4th pin
RXI <-> next up i.e. 5th pin
DTR <-> next up i.e. last pin

Other than that, I guess it may be something wrong with the way I made the board? If so, what's the best way to troubleshoot? Could it be a bad bootloader flash? Is there a way to check if the ATMega has a bootloader?

edit in fact, it could be because I don't have the Si7021 connected? Could this be the reason a sketch is not uploading successfully? :worried:

[m26872]

@rsachoc Start simple. Try on a board without nRF and sensors. Remove everything in the sketch and make it to just print "Hello world" back to serial monitor.

[rsachoc]

Thanks, I haven't actually built a new node, but have been double checking everything on my current node. One thing I wanted to confirm, the 4.7uf capacitor, does the negative leg have to be on the corner of the board, as this is the way I have it currently? I think looking at the board layout in the main slim node thread, it should be the positive leg on the corner and the negative leg on the side of the board (the short side of the board)?

[m26872]

@rsachoc I don't have it in front of me rigth now... but, there should be an arc and a super-small "+"-sign next to the positive pad. Maybe it just look like a dot.