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Chrisk

Senior Member

Joined: 21/12/2014
Location: Australia
Posts: 137

Posted: 11:56pm 31 Aug 2018

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Hi Guys
I don't know what I am missing here, it's obviously about pin allocation but I cannot see it.
I have two DS18B20 connected to pins 15 and 16.
I wanted to add a third to pin 9

Pins 15 and 16 work fine but I get an error when I use pin 9.

The test program is below.
' DS18B20 test program for maximite insitu - tmptest2.bas
' 31/1/2018
'
Clear 'clear any variables in memory
' Initalise I/O pins
Temppin = 9 ' DS18B20 pin
Setpin Temppin,2 ' Make it input digital
Probe = DS18B20(9)
N = 0
TT2 = 0
Do
TT1 = 0
N=N+1
TT1 = TT1 + Probe
Pause 100
If TT1 < 0 then
TTout = (-128 + 1) - Probe
TT2 = TT2 + TTout
else
TT2 = TT2 + probe
endif
Loop until N > 10
Pause 50
TT2 = TT2/N
Print TT2
End

Running it gives the following error:

[16] Probe = DS18B20(9)
Error: DS18B20 not responding

What am I missing?
I've checked the wiring and used two DS1820s.
Is it a problem with pin allocation?

Chris K

Chopperp

Guru

Joined: 03/01/2018
Location: Australia
Posts: 1106

Posted: 08:01am 01 Sep 2018

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Hi Chrisk,

I assume you are using physical pin 43 (pin 5 on con6) for DS18B20(9).

BTW, you do not have to initialise the pins or do anything else. It is done for you.

One of my lines of code is simply:-
Read_Temp = ds18b20(5) where (5) is physical pin 24 (pin 13 on con6).

I have used many other pins but not tried pin(9) but it should work assuming it is wired correctly with the specified load resistor.

Brian

ChopperP

Chrisk

Senior Member

Joined: 21/12/2014
Location: Australia
Posts: 137

Posted: 10:21am 01 Sep 2018

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Hi Brian/Chopperp

The pin 9 that I am using is the MMBasic pin 9 which should be correct. The other two DS18B20s are using MMBasic pins 15 and 16 as described on p6 of the Maximite Hardware Manual under the heading "Rear Panel I/O Connector" which has 26 pins.

Didn't realize I didn't need to initialize pin when used in conjunction with DS18B20.

Chrisk

Chopperp

Guru

Joined: 03/01/2018
Location: Australia
Posts: 1106

Posted: 11:16am 01 Sep 2018

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Hi Chrisk,

OK. There's a lot to learn (& forget)

. I assume you have looked at page 10 of the MMBasic Language Manual Ver 4.5.

If your are using MMEdit in MM Chat mode (or with the screen editor I think), you should be able to check the sensor operating by typing:-

Probe = DS18B20(9) <Enter>
print Probe <Enter>

or just Print DS18B20(9) should work.

It should give the current temp reading if it is working.

Use this method with one of the working ones first to make sure you can get readings.

You say you have swapped sensors around?

Are you able to temporarily use another pin? I also use some on the Arduino connector. (D11, 12 & 13)

I have actually used pin(9) in the past, so it should work.

Brian

ChopperP

Chrisk

Senior Member

Joined: 21/12/2014
Location: Australia
Posts: 137

Posted: 03:03am 03 Sep 2018

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Thanks for the tips Brian
Helped me solve the problem.

I had these probes on a 3m cable with 3 wires, yellow, red and black.
I had joined the red and yellow and used the black as the 0V.
That was a mistake. Should have joined the red and black for 0V and yellow for the data.

Had I not used heat shrink over the joins of the other two I would have noticed.
I shouldn't have assumed connections for operation in parasitic mode.

Thanks for your responses.

Chris K

Chopperp

Guru

Joined: 03/01/2018
Location: Australia
Posts: 1106

Posted: 04:32am 03 Sep 2018

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Great news Chris K. Glad I could help

Brian

ChopperP

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