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Wireless Sensor Node with MSPG2553 and 8-pin NRF24L01+ module


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This is my first time designing a PCB for MSP430. I really like the NRF24L01+ booster pack but I would like something smaller to use for remote temperature sensors. With that in mind I've designed a 2

Here's my variation of a wireless sensor node... this was inspired by a need to monitor temperatures throughout the house; I have 6 of these boards from OSHpark I just got today!   http://spirilis.n

The PCBs arrived from Elecrow a couple of days ago and I populated the first one. This may be the first time I have successfully soldered a TSSOP.     This one is configured with a 3-pin SIP head

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After a lot of unproductive messing about I finally have 2 launchpads talking temperature to each other over a radio link. I feel like I am over the hump with this project.

 

The problem was something I found obscure. msp430-gcc required more header files than I was including but wasn't giving compile errors. This might have been something to do with combining C and C++ source files. I fumbled my way through but it took me an entire evening to find the solution.

 

No fault of Eric's wiki, which is exemplary.

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So I have finally got 2 of my "Magic Mote" wireless sensor nodes talking over the radio waves. I ended up porting the DHT22 library I was using to C, it was easier than farting about trying to work out why I couldn't get C++ to compile properly with msp430-gcc.

 

When I tried to access the hardware UART on the receiving board, I realized that I had labelled the RXD and TXD pins according to the Launchpad "software UART" orientation, i.e. the wrong way around for hardware UART. Oh well, never mind.

 

All I have to do now is work out some kind of protocol for setting the desired temperature and then hook the receiving mote up to the furnace relay that I made, and I have a radio controlled thermostat for the house. Oh, and then write it all up before 12pm for POTM!

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The Magic Mote wireless temperature sensor is working well and communicating with a second Magic Mote that is receiving the temperature signal and using it to control the furnace via a 2-coil latching relay. 

 

Documentation (works in progress):

 

Github repository: https://github.com/t0mpr1c3/furnace-relay.git

 

Blog post: http://smokedprojects.blogspot.com/2013/12/magicmote-thermostat-and-wireless.html

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Version MO02 is in the works with a couple of superfluous components removed and an isolated ground plane under the watch crystal.

 

I'm not sure if there is any demand but I would be happy to get a batch of 20 made up for the 43oh store. Otherwise I will probably wait until after Chinese New Year and squeeze a batch onto the edge of a larger panel.

 

Edit 19th Jan: I am sold out at Tindie so I will order more this week.

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You don't really need the external crystal. Getting rid of that can save you a lot of space which may allow you move your tactile button to an accessible location. Have you tested the range of your module? I'm working on something similar and found even with 250kbps it won't fully cover the whole range of my house in which case there are some bits flipping and I finally implemented an error correction algorithm to ensure max range with good quality.

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The crystal is going to stay, it is used to time the sleep of the sensor node and will be handy to give accurate time stamps.

 

The button is certainly something I am looking at. I have removed 3 components which has freed up some space. I am also looking at some smaller SMD switches that could squeeze in elsewhere. I may also decide to orient the radio module differently. I haven't decided yet. The button position is a factor, but probably not the most important.

 

Edit: I changed the programming header to 2x3 footprint and squeezed a SMD switch in at the side.

 

I have found the range satisfactory so far running at 1 MHz IIRC. There are dead spots here and there as you would expect. If I really need to put a sensor somewhere inaccessible and can't relay the signal from another node then I will look into using a better aerial.

 

How did you have the CRC configured on the Nordic module? Were you getting errors that the CRC was not picking up?

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It's pretty funny, after boasting today about the temperature data I collected with my army of sensors (soldered 2 more up last night & stuffed them up in the sill/rimjoist to monitor the temperatures while the woodstove was cranking) I got a coworker asking me to quote him out a whole army of sensors + nRF24 base station for his house he just bought...

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haha, I have been considering designing an nRF24L01+ cape.  Seems like a waste given the simplicity of it vs. the cost of the PCBs.  Also curious about how the software layers would work... I'm not sure what type of Linux kernel network "layer" or subsystem this would fall under, although I guess something like it has been done before.

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Version MO02 is in the Github repository. It features a more accessible tactile switch and IDC6 compatible programming/serial header.

 

I have lots of PCBs available in the Tindie store but I am always happy to trade. Or PM me for a sample if you are doing something interesting - you might catch me in a good mood ;)

 

post-26958-0-99808500-1393356680_thumb.png

 

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