Few questions about logic level converters to rfm69hw

[tjohansen]

Hi

Im a total newbie at arduino, but it has fascinated me for a while and the Uber Home Automation guide, kinda pushed me to get started.

But a bit too late, after I had bought some 5v's arduino clones, and afterwards read alot about switching to 3.3v, I finally discovered this great forum.

I can see there are alot of reading ahead, have read some, but Im so eager to get started and to correct my faulty buys, that I hope you can point me in the right direction.



I have alot of questions, but a plan first is properly more appreciated.

Primary objective:

I want to monitor temperature and humidity in every room and outside.

- I have a working Rpi with openhab up and running, (still need the MQTT part, but Im not worried about that, Im a linux guy so I figure it out.)
- I have bought some RFM69HW 868 mhz transceivers from Holland (im Danish so bying in EU is the cheapest)
- I have 3 Dccduino uno R3 5v, (not switchable, but it has 3.3v volt pin but thats not good enough for the rfm69hw, I have read)
- I have some DHT11 senors.
- I have a ethernet shield.
- I have breadboards etc.

As I have been reading, I have now figured out that the pro mini's are preffered, both due to size but especially to the 3.3v part. So in the future I properly will buy the pro mini's.
But now I need to get it working first.

So to my first questions:

1. Is Computourist's Github archive the preffered source and "easy" enough to follow without hitting the wall over and over again? Ofcourse start out simple and then learn on the way.


2a. Hopefully I can use my arduino uno r3 clones by adding Logic Level Converters between the arduino and the rfm69hw, with your help....... Because I cant figure out how to connect the wires without frying the rfm69hw.

2b, will there be a power problem when connecting the rfm69hw to the arduino, because I have read alot about the transceiver need too much power, more than 100ma?




I have made a sketch of the wiring that I cant figure out, (if the LLC is a working solution)
I have read that only power and the inputs to the rfm69hw needs to be converted to 3.3v, the outputs from the rfm69hw dont need to go through the LLC, correct?.




   



I hope you can help me. If I can get this working, I have some more interesting fun stuffs like monitoring my heatpump flow temps, power measurings, controlling garden lamps, fountain etc.

So much potential.



Thomas Johansen

[greginkansas]

If you are a software guy on your next order try these www.anarduino.com/product.jsp . I made the first two these are good. I would not use the 3V from the UNO not strong enough. Use the level converter on all data lines.

Greg

[tjohansen]

already have bought the rfm69hw from this dutch company in europe: www.hoperf.nl/Webwinkel-Category-3075967/RFM6x-modules.html

I can buy the logic level converters "cheap" here in denmark, but dont know how to do the wiring.

[computourist]

Hi tjohansen ,

although level shifters might work for nodes, I doubt they will work for the MQTT-gateway.
In the gateway two devices (ethernet&RFM69) compete for control of the SPI-bus. For this to work each of the devices need to have their outputs 'floating' when not in use, so the other device can control the bus. Most level shifters only have an "ON" and "OFF" state and are not capable to leave the bus floating.

If you are handy with a soldering iron I would recommend changing your UNO's to 3.3 Volts, as described here.

Success !

[tjohansen]

computourist, valuable info from you and in that guide, think I will try on one of the three I have.

[greginkansas]

Computourist, I must have got lucky, I used a sparkfun level converter on my gateway with a mega and it works.

Greg

[kmac]

I also use level converters on my Arduino Uno gateway for all signals to/from the RFM69hw. Haven't had any issues.

[tjohansen]

Greg and Kmac, thats good news to me, makes it more simple, thanks for your feedback

[tjohansen]

could one of you show how you wired it, from the arduino to the LLC and then to the rfm69. That would help me alot.

[computourist]

Good to hear I was too cautious ;-)

[greginkansas]

I had this saved
note on the uno I made a 3.3V supply

If you have a bare RFM69W that you want to connect to an Arduino, you might use these connections (untested): CAUTION: you must use a 3.3V type Arduino, otherwise you will also need voltage level shifters between the Arduino and the RFM69. CAUTION, you must also ensure you connect an antenna
* Arduino RFM69W
* GND----------GND (ground in)
* 3V3----------3.3V (3.3V in)
* interrupt 0 pin D2-----------DIO0 (interrupt request out)
* SS pin D10----------NSS (chip select in)
* SCK pin D13----------SCK (SPI clock in)
* MOSI pin D11----------MOSI (SPI Data in)
* MISO pin D12----------MISO (SPI Data out)
*

[kmac]

tjohansen, this is how its wired:
5v,3.3v and GND from Arduino to HV,LV and GND on 2 logic level shifters
Arduino Interrupt 0 (D2)--HV1,LV1-- RFM69 DIO0
Arduino SS (D8) --HV2, LV2-- RFM69 NSS
and so on for all signals.

You connect the Arduino pin to an HV(1-4) on the shifter and the LV(1-4) goes to the RFM69 pin. Just match them up (HV1-LV1, HV2-LV2, etc).
Since there are 5 signals to be converted you need 2 of the logic level shifters.

Dont forget, if you are using the Ethernet shield it uses Arduino pin 10 for the select signal so the RFM69 NSS select line will need to be on a different pin. I have mine connected to Arduino pin 8.
Then make sure your Gateway sketch has the proper pin# for the line shown below:
#define RFM_SS 8     // Slave Select RFM69 is connected to pin 8

[tjohansen]

Thanks for the guidance, unfortunately I wont have the time to try it out until mid next week, but can wait to try.



So glad I found this forum :-)

[tjohansen]

Hi finally got time to look at it.


It makes more sense now, but still have a question, just to be sure and play it safe.

Have set it up like in the picture below, just to make sense and visualize it, I havent soldered wires to the RFm69 yet or added the antenna.



Question:
now that there are two level shifters, should both be getting GND and 5V? or is it just ok as in the picture where the bottom level shifter does not have GND and 5v?

[kmac]

Each level shifter module has GND, HV and LV. These need to be connected to ground, 5v and 3v on each of these modules.
The HV and LV on each module provide the reference voltage for the high side and low side to work properly.
You can just run a wire from each of these on your first module to the corresponding pins on the second module.

The LV pin should be conneced to a 3.3v source on your Arduino. It can not be used to power the RFM69 as it is a reference input only.

[greginkansas]

If you get weird things happening the 3V pin gives 50 mA not 100+ for full power

[tjohansen]

I see, sorry for not having discovered that before, just haven't though of it in that way, my "logic thinking" skipped the step of looking up Logic level shifter diagrams. It's explained perfectly here www.pololu.com/product/2595, though this LLC does not have gnd as mine have.

I'll set it up tonight.
And show you, just to be sure.

I really appreciate your inputs.

[tjohansen]

think I got it now?

the picture of logic level converters shown here are not bi directional but mine are and have same layout, thats why I used these as "stand in" .

I have used D8 because this is for the gateway with ethernet shield.
I looked at papa's image of the gateway and saw he had added two diodes for gateway status. I must add those too, so gonna look into his schematics for guidance.



EDIT: picture below have been updated to correct wiring as mentioned by Kmac

[kmac]

Looks good except you need the 5v going to the top module HV pin.
The level shifters I am using are also the bi-directional ones.

[papa]

tjohansen, The Gateway LEDs are from computourist's Gateway schematic. My only change is to use 100 ohm resistors with the LED so they burn brighter, but are still protected from burning out. As I corrected in my Success... thread:

For each of the signal LEDs, (maybe applying heat shrink tubing to protect the bare wire leads) solder a resistor to the LEDs longer wire lead (the plastic LED base above that lead is usually round). Plug one LED's resistor into the Ethernet Shield's D7 & its shorter free LED wire lead in a Gnd socket on the other side (the plastic LED base above that lead is usually flat).  This first LED's steady shine will indicate the gateway is connected to the MQTT service on the computer. Plug the other LED's resistor into the Ethernet Shield's D9 & its free LED wire lead in a Gnd socket on the other side. This LED flashes to indicate radio signals being sent.). (Resistor & LED leads are small gauge & fit loose in sockets. You can "bulk them up" by spreading some solder along each end. Experiment with amount until lead solidly enters & stays in socket.) (The Gateway would work without LEDs, but with them, it's easier to see that it is working.)

[tjohansen]

Feb 19, 2016 22:26:55 GMT kmac said:

Looks good except you need the 5v going to the top module HV pin.
The level shifters I am using are also the bi-directional ones.

Ofcource, my mistake, about the 5v, forgot to draw it, but did it correct on the real board :-)



 

[mova]

How did this work out?

I've been searching for ways to connect an RFM69HW via LLC but there seems to be minor differences everywhere I look.
In this Sparkfun tutorial under Using the LLC for SPI They don't seem to have common-grounded the two sides like you have.

under Using the LLC for Serial  There is no 3.3v wire from arduino to the SD-module. Why can the LLC convert 5V>3.3v here but not in SPI?


Well... Actually I'd just like to know it the wiring you posted worked out

[jimkernsjr]

tjohansen:

I've made exactly your mistake before too - bought all of it before I learned it needed 3.3v signals and not just voltage, and that the 3.3v line is too weak. The Uno Bruno LC works great - I bought that for a gateway and kept all my "mistakes" for nodes and other experiments...

A few other ways that worked good for me:

The 74HC4050 on a shield with a voltage regulator(use just the 5v line that has enough ma (works great with a non-switchable Uno):
jeelabs.net/boards/6/topics/4144

This makes it easy to build:
www.ebay.com/itm/1x-Prototype-PCB-for-Arduino-UNO-R3-Shield-Board-DIY-Combo-2mm-2-54mm-Pitch-/131398518268?hash=item1e97f645fc:g:atEAAOSw1vlUriGi


I have purchase some of these too:
oshpark.com/shared_projects/bJRprI06
or search for RFM69 breakout on Oshpark.

These work with voltage dividers...not needing level shifters...but you still have to contend with the power line.

Hope it can help you!