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Forum Index : Microcontroller and PC projects : using HC-12
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palcal Guru  Joined: 12/10/2011 Location: AustraliaPosts: 1970 |
My first time trying to send data from one MM to another. I have the HC-12s connected and I know they work because I have used them as a serial link. I'm not having much luck. On the send side I have OPEN "COM1:9600" as #1 PRINT #1, X$ on the receive side I am not sure how to use INPUT or LINE INPUT can someone give me a short snippet of code to show how it is done. I have spent all morning going through the manuals and tried many things but the best I received was a Y with two dots above it. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6230 |
Y with two dots sounds like a baud rate mismatch. On the receive side you can set up an interrupt to trigger with a set number of characters or with the latest MMBasic, you can use a specific character to trigger the interrupt. This save polling the com port looking for the CR OPEN "COM1:9600, 256, MyInt, =13" AS #1 DO:LOOP SUB MyInt x$ = INPUT$(LOC(), #1) end function I think thats right. Jim VK7JH MMedit |
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| erbp Senior Member  Joined: 03/05/2016 Location: AustraliaPosts: 195 |
I think the line x$ = INPUT$(LOC(), #1) should be x$ = INPUT$(LOC(#1), #1) Cheers, Phil. Update: and End Function should be End Sub |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9511 |
Yes, that is pretty much how I do it for line-at-a-time. The beauty of the MM serial port buffer, is that it will take care of any data that arrives, and all you have to do, is check the buffer as part of your main loop and act if there is anything there.  For byte-at-a-time receiving, I use something like this: [code] If LOC(#1)<>0 then DO D$=INPUT$(1,#1) 'Suck a byte from the buffer T$=T$+D$ 'Add byte to string Loop Until D$=CHR$(13) ... [/code] In the example above, I am looking for an EOM(end of message) marker byte. It can be anything, but I tend to just use CR.(decimal 13) The MM buffer is really awesome for this kind of thing, as the messages are then self-queuing in the buffer(provided you make sure the buffer is big enough), and you just read the messages out one after another to process them. The code does not need to worry about missing a message while you are processing the last one, as the buffer will take care of all of that for you. Smoke makes things work. When the smoke gets out, it stops! |
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| viscomjim Guru Joined: 08/01/2014 Location: United StatesPosts: 925 |
Hey Grogster, you seem to be the HC-12 slayer, I have ordered a few of these from one vendor and I think they are genuine. However, if not, I know to only use units from the same vendor due to the weird off freq. stuff you discovered in another thread. I would like to run these on 3.3v as I don't want to have to add more components for 5v just for this module. Do you find these work o.k. on 3.3v, or is this an "iffy" thing to do? What have you experienced... Just for fun I also ordered a few of THESE. (The 915Mhz Version). It seems like I can get a bit of distance with these and they are spec'ed to work on 3.3v which is great. I plan on running these between two warehouses that are about 1.5 miles apart to control a few things with, of course, a micromite. They are sitting on my bench just waiting for a bit of play time. Have you ever tried these? |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9511 |
Hey there Jim. I DON'T recommend running the HC12 on 3v3. The PDF says you can, but I have found them to be flaky at that voltage. The input supply is stated as 3v2 to 5v5, but as 3v3 is only 100mV above the minimum voltage, there is only a tiny amount of headroom there, so your 3v3 supply needs to be VERY clean, and rock-solid. Any kind of voltage-drop on the 3v3 rail will cause the HC12 to get confused and do odd things due probably to the brown-out effect. I run all my HC12s on 5v, and just use a 5v tolerant COM port. If you don't have any spare 5v COM ports, you can get very cheap bi-directional level shifter things on eBay to allow you to put the 5v into a 3v3 pin, and to translate the 3v3 back to 5v for the module. See this link for an example, and these things work beautifully to get around the 3v3 vs 5v0 logic for MCU pins. Those LoRa modules you found look interesting. What did you pay for them? There is no price on the webpage. EDIT: I've just had a quick look at the specs of these things, and they are quite impressive, really. Supposedly have FCC approval, although, that might just be sales talk. A -148dBm receiver sensitivity is excellent if it really is that. This would make them very good listeners indeed.  -4dBm to +15dBm adjustable output power, 868MHz/915MHz, up to 15km range on a good day. Nice find, Jim. I like them.  Smoke makes things work. When the smoke gets out, it stops! |
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Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1636 |
You can find them on eBay here Bill Keep safe. Live long and prosper. |
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| viscomjim Guru Joined: 08/01/2014 Location: United StatesPosts: 925 |
Grogster, I paid $15 a piece for those modules. A bit pricey, but for the distance I am anticipating, it was worth it. I believe you can buy just the SX1276 for less than half that, but reyax put a nice little mcu on the board to let you use a serial port with simple AT commands. The SX1276 uses spi and looks a little confusing to me. I checked out the arduino library (radiohead) for this to see if it could be ported to mmbasic, but way over my head, so the mcu + SX1276 for $15 was worth it to me to start using them. I do believe they are truly FCC approved from what I can read on line. There is also an SX1278 for 433Mhz. I also ordered a couple of THESE at 1 W and THESE at 100mW. Both of which are apparently FCC approved. They use a different setup, but I found documentation for using them. Both use uart also. Look on Youtube for the reyax units, they seem to work quite nice... especially THIS ONE. Also check out TTN network. Very interesting stuff. I think there was a shedder that uses these or something very similar to them (srnet???). I believe he did the satellite for $50 or something of that nature. I will do a search on TBS to see if I can locate that thread. I also believe he used something like these. On the HC-12... Thanks for the info, looks like 5v it is. After a bit of googling, I see that at 5v they recommend using a diode to drop the voltage a bit if you are planning on transmitting a lot to keep the on board reg. cooler. Is this something you've noticed being necessary? |
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OA47 Guru Joined: 11/04/2012 Location: AustraliaPosts: 982 |
I have purchased around 20 of these units over the past year from many different suppliers on Ebay and Aliexpress and I have been having trouble with some of them working in a network. I am wondering if there is a similar situation with cloned units from other sources. There seem to be some with the E-byte branding, V1.0, V3.0 and V6.0 as well as some without the E-byte brand that have the same model number.  Has any one else had any issues? OA47 |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1970 |
OK all good nearly, I got the HC-12s talking but I am wanting to send 3 values so to send I have PRINT #1, X$, Y$, Z$ How do I receive this and place it into 3 variables. One thought was to look for the comma? Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6230 |
Does the length of the three variables vary much? One simple method I use is to format the data as fixed length strings so I can use MID$() to slice it up. It also looks nice when printing out, neatly aligned, ready for copy/paste into other programs If you are keeping it within MMBasic, you should be able to use INPUT #1,var1$, var2$, var3$ I haven't tried this in combination with the serial port interrupt. Jim VK7JH MMedit |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1970 |
That gives me something to work on, Thanks Jim. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1970 |
I took your advice Jim and formatted the 3 strings then sent them as one string and broke the string up on the receive end. Works perfect. Thanks. Edit... Just found the sleep current of the HC-12 is 22uA so with an Armmite L4 and E-Ink display should be able to make a decent battery powered project. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9511 |
You only really need the series diode to drop 0.6v or so to relieve the heat stress on the LDO regulator on the module, IF you are transmitting a continuous stream of data - like a 100% duty cycle. If you are only transmitting sporadically or with a 50% duty cycle or less, you don't need the diode. Smoke makes things work. When the smoke gets out, it stops! |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1970 |
I have got my HC-12's talking OK. But on the receive end the data does not change when it updates. At the moment for testing I have it updating every minute. I close the COM port at the end of the loop wait 60 secs. then loop and reopen the COM port, but when I input the data it is the same as before. If I switch off and then on again I find that the data is updated. I thought that closing the COM port cleared the buffer. What am I doing wrong. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9511 |
Closing the COM port does clear the buffer. Can you post your two codes? One from the transmitting end, the other from the receiving end. Smoke makes things work. When the smoke gets out, it stops! |
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| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1970 |
Ok here it is, my coding is maybe not the best. This is the SEND code SetTick 30000, RESET 'resets rain to zero at 9:00am RTC GETTIME Dim Temp,Hum Dim Information$ Dim rain,R$,RY$,RM$,T$,H$ SetPin 18,CIN ' pin connected to rain gauge 'VAR RESTORE Do Open "COM2:9600" As #1 HUMID 2, Temp, Hum ' get Temp and Humidity from DHT22 Temp=Cint(Temp) Hum=Cint(Hum) T$= Str$(Temp,2) H$= Str$(Hum,2) Print Cint(Temp);" ";Cint(hum) Print Time$ Rain=Pin(18)*.45 ' convert gauge tips to mm. rain=55 'rain gauge not connected(for display setup) R$=Str$(rain,3) RY$=" 55" ' rain yesterday for display setup RM$="172" ' rain month for display setup Information$=T$+H$+R$+RY$+RM$ ' convert data into one string Print Information$ Print #1, Information$ Pause 500 Close #1 'VAR Save RM$ ' to save rain data if power lost Pause 30000 Loop Sub Reset If Left$(Time$,2)="09" And Mid$(Time$,4,2)="00" Then RainY = Rain RY$ = Str$(RainY,3) RainM = RainM + Rain RM$ = Str$(RainM,3) Rain = 0 Pin(18) = 0 RTC GETTIME EndIf End Sub This code also has the DHT22 C code at the bottom And this is the receive code CLS ' Setup the E-Ink display Box 0,0,MM.HRes,MM.VRes Text 20,MM.VRes-145,"TEMPERATURE HUMIDITY",RMU,2,2 Text 40,280,"In",RMU,2,2 Text 60,275,"Out",RMU,2,2 Text 90,140,"RAIN YESTERDAY MONTH",RMU,2,2 Refresh Do Open "COM1:9600" As #1 Do If Loc(#1)<>0 Then D$=Input$(1,#1) Information$=Information$+D$ ' Information$ contains all the data EndIf Loop Until D$=Chr$(13) Close #1 Temp$=Left$(Information$,2) 'split up information$ to regain data Hum$=Mid$(Information$,3,2) Rain$=Mid$(Information$,5,3) Rain_Yesterday$=Mid$(Information$,8,3) Rain_Month$=Right$(Information$,4) Print Temp$;" ";Hum$;" ";Rain$ ' send data to E-Ink display Text 60,150,Temp$+"c "+Hum$+"%",RMU,2,2 Text 125,140,Rain$+" "+Rain_Yesterday$+" "+Rain_Month$, RMU,2,2 Refresh Pause 60000 Loop Also the line VAR RESTORE in the send code throws an error so it is commented out. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| erbp Senior Member Joined: 03/05/2016 Location: AustraliaPosts: 195 |
You need to clear the data you have accumulated into Information$ on the first receive cycle before starting the next cycle. I suggest you add the following line immediately prior to the Pause 60000 at the end of the loop in your receive code: Information$ = "" Cheers, Phil. |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6230 |
You might need when you open the serial port otherwise you are just adding the new data onto the end of the old. Edit: Typing too slow! VK7JH MMedit |
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disco4now Guru Joined: 18/12/2014 Location: AustraliaPosts: 983 |
In the receive code I think you need an Information$="" at the end of the loop. Now I think it continues to append and your keep pulling the same data off the front of the string. It probably eventually grows bigger than 256 bytes and errors if you let it run long enough. Regards Gerry PS Too Slow! PS again: Honest Jim , I didn't copy. Latest F4 Latest H7 FotS |
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