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Bizzie
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Joined: 06/07/2014
Location: Australia
Posts: 192

Posted: 11:26am 15 Jan 2015

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Background:
I have had a system of Picaxe 20X2�s working as low speed counters for about 4 years.
It consists of one PicAxe acting as the master and up to 5 slave devices. Each of these 5 devices monitor 12 pins for contact closures (reed switches). The slaves write their data to the scratchpad memory and this is then read by the master and transmitted via the serial port to a PC.
The client (well really my son involved in university research) wants to now receive that data by email once a day.

My solution:
Replace the master with a CGColorMax2-B so I can use an ESP8266 to get an internet connection and also have the benefits of the SD card and RTC
My problem: I can not get the MM and a slave PicAxe 20X2 to �talk� via I2C.
I am certain there is no connection problems on the CGColorMax2-B as I can use a MicroMite as a slave successfully using the code on page 55 of the MicroMite 28-pin chip User Manual Ver 4.5 by Geoff Graham.
When I replace the MM28 with the picaxe and use the program below I can not read the data I have placed on the scratchpad of the picaxe (PUT 0,0 PUT 1,1 �.. PUT 9,9). The picaxe has been put into slave mode as I have done successfully for the last 4 years.

Dim a(3)
I2C OPEN 100, 1000
I2C READ &H38, 0, 3, a(0)
For I = 0 to 3
If MM.I2C then
Print �READ failed�
else
Print a(i)
endif
next
I2C CLOSE

Pressing F2 results in :-
0
0
0
0

Picaxe slave I2C methods are quite different to the methods used in the MM�s, there are no interrupt routines defined so I do not know what is going on in the picaxe. As stated above you merely read the portion of memory called the scratchpad!

My questions:

Has anyone set up such a system?
Can anyone suggest where I go from here to find why I do not see actual data?
I would prefer not to have to completely produce an MM only solution.

Rob White

Grogster

Admin Group

Joined: 31/12/2012
Location: New Zealand
Posts: 9586

Posted: 01:27pm 15 Jan 2015

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Hi there.

If MM.I2C then This syntax looks wrong to me. If/Then needs a reference point, such as something like If MM.I2C=0 then kind of thing.

Smoke makes things work. When the smoke gets out, it stops!

Geoffg

Guru

Joined: 06/06/2011
Location: Australia
Posts: 3282

Posted: 01:41pm 15 Jan 2015

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Grogster said If MM.I2C then This syntax looks wrong to me. If/Then needs a reference point, such as something like If MM.I2C=0 then kind of thing.

That syntax is OK. The IF command evaluates the expression and treats the result as false if it is zero and true if it is non zero. The simplest expression that you can have is just a variable, so in this case the IF statement will be true if MM.I2C holds a non zero number.

If you choose variable names carefully this syntax makes for very readable code. For example:

IF DoorOpen THEN ...

Geoff

Geoff Graham - http://geoffg.net

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6266

Posted: 02:12pm 15 Jan 2015

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What addres do you have the Picaxe set to?
I have never use I2C on the picaxe but if I read the syntax correctly, Picaxe would need an address double the Maximite address value.

Picaxe includes the R/W bit while Maximite adds it to the address.

This is an area that cause much grief. There isn't any definite 'right way' to describe the chip address. Evert data sheet has a different way of doing it.

Jim

VK7JH
MMedit

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9586

Posted: 02:26pm 15 Jan 2015

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Geoffg said

Grogster said If MM.I2C then This syntax looks wrong to me. If/Then needs a reference point, such as something like If MM.I2C=0 then kind of thing.

So noted.
I stand corrected.

Smoke makes things work. When the smoke gets out, it stops!

WhiteWizzard
Guru

Joined: 05/04/2013
Location: United Kingdom
Posts: 2932

Posted: 11:37pm 15 Jan 2015

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As TassyJim says, my money is on an 'incorrect' address (assuming hardware is setup correctly).

If you have a logic analyser then this is easy to check - if not then just double check the data sheet / manual to ensure you have the correct address formatted correctly.

Good luck . . . . .

WW

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