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Forum Index : Microcontroller and PC projects : Maximite - Picaxe, Serial / RS485 Comms
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| nasi Newbie  Joined: 08/07/2015 Location: AustraliaPosts: 16 |
Hello All This is my first post, I apologize in advance if there is a thread already covering this, however extensive browsing has eluded me to some light of help. I am attempting to build an rs485 network around my house to control and monitor various attributes of our off grid setup. My micro controllers of choice are maximites and picaxes as I have a surplus in the workshop. So to cut to the chase I am struggling with Sending data from a maximite to a picaxe. I have been reading the SNAP / Scaleable Node Address Protocol for inspiration and have had some success. Currently I have been able to accurately control a picaxe 08m2+ with 4 relays no problems I then increased the RS 485 network to a third node with a picaxe 18m2+ I practically took the same code from the 08m2+ and modified it to reflect the 18m2+ configuration. The pickle I am in is that for some reason the 18m2+ simply does not want to co-operate in the same fashion as the 08m2+ which is weird and I am messing with baud rates, pauses and chip freq without any idea why the 18m2+ under the same environment will not logically function. The issue seems to be centered around the serin command -------------------------------------------------------- 08m2+ serin 3,T4800,(SYNC),HDB2,HDB1,DAB1,SAB1,DB1 'debug 18m2+ serin b.6,T4800,(SYNC),HDB2,HDB1,DAB1,SAB1,DB1 debug -------------------------------------------------------- The basic bytes of data I change respectively to poll the nominated controller. As I said the 08m2+ works great if I remove the qualifier brackets for the 18m2+ when debugging I can get some data in but it comes through wrong the sync byte may sometimes show up correctly or in the wrong variable but its so inconsistent. I have removed the 08m2+ from the equation to just test between the maximite and the 18m2+ still no success. Anyway I hope this is enough info to get started and I appreciate anyones input. Once again apologies for any lack of forum etiquette on my part. PS, I am using the little MAX 485 modules Link here should provide an image of the module: http://www.aliexpress.com/item/Precise-MAX485-Module-RS-485-TTL-to-RS485-MAX485CSA-Converter-Module-For-Arduino-Integrat ed-Circuits-Products/32309776786.html Happy to provide more info if needed. Cheers Ladys and Gents Richard |
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TassyJim Guru  Joined: 07/08/2011 Location: AustraliaPosts: 6269 |
Hello and welcome. Some users have found that a delay between bytes is helpful when sending from maximites/micromites to picaxes Using two stop bits is the easiest way to achieve the delay. I am not sure if the above is relevant for rs485. Jim VK7JH MMedit |
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| nasi Newbie Joined: 08/07/2015 Location: AustraliaPosts: 16 |
Jim Thank you very much for such a prompt reply. Forgive me could you elaborate on how you would implement the stop bits, My MM code for testing is as: -------------------------------------------------------------------- Dim DBYTE(5) DBYTE(0) = 250 ' SYNC BYTE DBYTE(1) = 80 ' HEADER DEFINITION BYTE 2 DBYTE(2) = 1 ' HEADER DEFINITION BYTE 1 DBYTE(3) = 50 ' DESTINATION ADDRESS BYTE DBYTE(4) = 255 ' SOURCE ADDRESS BYTE DBYTE(5) = 1 ' DATA BYTE (COMMAND / FUNCTION / DATA) menu: Cls Print "1, Send Packet" Print " " Print "6, Quit Program" Print " " Input cmd If cmd = 1 Then Send_PCKT If cmd = 6 Then End Cls End EndIf GoTo menu Sub Send_PCKT Open "com1:4800, DE" As #1 For i = 0 To 5 Print #1, Chr$(DBYTE(i)); 'Pause 50 Next Close #1 GoTo menu End Sub -------------------------------------------------------------------- Thanks again Jim |
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Bill.b Senior Member  Joined: 25/06/2011 Location: AustraliaPosts: 235 |
hi Nasi This is a sample program I used to send data to a picaxe 14m2 (oled display 4 Line) [code] OPEN "COM1:2400, INV, S2" as #1 pause 30 Print #1,chr$(254) + chr$(1); pause 30 Print #1,chr$(254) + chr$(128); ' line 1 Print #1,"Hello world "; Print #1,chr$(254) + chr$(192); ' line 2 Print #1,"What a great Day"; Print #1,chr$(254) + chr$(148); ' line 3 Print #1,"to be alive"; [/code] Bill In the interests of the environment, this post has been constructed entirely from recycled electrons. |
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| nasi Newbie Joined: 08/07/2015 Location: AustraliaPosts: 16 |
Bill Thank you And Thank you also Jim. It does seem impossible until it's done. |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6269 |
I am not sure what the DE line does between characters of if it matters. Here are two options to try The first is your code with S2 in the initialise string. You can play with the pause between characters as I assume you have been doing. The second builds the data into a string and then sends it in one go. This way the DE control line behaves as I think it should. Jim VK7JH MMedit |
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| nasi Newbie Joined: 08/07/2015 Location: AustraliaPosts: 16 |
S2.... ahhh ok of course thats in the manual, :) Jim thank you for this. I will experiments and see how I go. Thank you again also Bill. |
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| nasi Newbie Joined: 08/07/2015 Location: AustraliaPosts: 16 |
I figured it out Gents. Just to give you some feedback. It ended up being these ttl to RS485 modules. I picked up a bunch of them online for cheap and it is starting to look as though they have somewhat of a failure rate. But thank you all anyway. Look forward to threading more in future. Hopefully I can return the favour. |
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redrok Senior Member Joined: 15/09/2014 Location: United StatesPosts: 209 |
Hi nasi;What RS485 modules are you using? I have been just using EXAR SP485 and SP485E chips. redrok |
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| nasi Newbie Joined: 08/07/2015 Location: AustraliaPosts: 16 |
I sent you a private message Redrok Apologies in advance if breaking etiquette. I will check out those chips, I picked these other units as they are fairly ready to hook up and obviously cheap. Look forward to speaking more. Cheers Richard |
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| Bill.b Senior Member Joined: 25/06/2011 Location: AustraliaPosts: 235 |
Hi nasi When I connected a pic32mx170 to C5 (pin4) of the 14m2, I did not use any interface modules. I connected the output of the 170 via a 100ohm resistor to the input of the 14m2 and all worked OK. Bill In the interests of the environment, this post has been constructed entirely from recycled electrons. |
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| nasi Newbie Joined: 08/07/2015 Location: AustraliaPosts: 16 |
Hey Bill I have not done much Pic programming in C but that sounds very interesting. I was concerned about the distance that data could be sent as I need to send around my property up to a possible 100m I have connected some of these micro controllers up directly at TTL levels but I was under the assumption they could not handle long runs nor was it safe to do so just in case of cable potential buildup. Please correct me if I am wrong. Speak again soon Richard |
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