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Cremo
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Joined: 21/07/2015
Location: Italy
Posts: 36

Posted: 08:58am 01 Oct 2016

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Hello,
I have problems interfacing the MCP3302 A-D converter using SPI port.
My test program is the following:

_____________________________________________________

option explicit

'Chip Select A-D
const CS_MCP3302 =14

dim integer dati(3) 'to receive 3 bytes

'configure pin as Chip Select of MCP3302A
setpin CS_MCP3302,dout 'pin as digital out
pin(CS_MCP3302)=1

settick 500, Read_A_D 'periodical reading

do
'''
loop

sub Read_A_D ' ADC reading
SPI open 1000000,0,8
pin(CS_MCP3302)=0 'chip select
spi write 3,&B00001100,&B00000000,&B00000000 'to configure chip and convert
spi read 3,dati()
pin(CS_MCP3302)=1 'chip unselect
spi close

print "data0=",hex$(dati(0))
print "data1=",hex$(dati(1))
print "data2=",hex$(dati(2))
end sub

______________________________________________________-

I see meaningless values printed.
If I connect a scope with SPI decoding I see correct values on it.

Maybe some problem in spi read from Micromite Basic ? The version I us is the 5.2 Plus version.

Thank you.

Pietro

matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 10209

Posted: 09:09am 01 Oct 2016

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Looking briefly at the datasheet I would say you need Mode 3 rather than 0. There is definitely no problem with SPI in 5.2

Cremo
Newbie

Joined: 21/07/2015
Location: Italy
Posts: 36

Posted: 09:35am 01 Oct 2016

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Hi Matherp, thank you for your fast reply.

Changing the mode does not help.
For example if I input to the A-D a voltage to obtain a 1023 value (HEX 3FF),
I see the following values: data0= HEX FF, data1 = HEX E0, data2 = HEX 00.

Best regards.

Pietro

panky

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Joined: 02/10/2012
Location: Australia
Posts: 1114

Posted: 04:41pm 01 Oct 2016

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Pietro,
Maybe a bit order problem? If you are receiving lsb first then ff e0 00 becomes 00 03 ff? Just a thought.
Doug.

... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it!

Cremo
Newbie

Joined: 21/07/2015
Location: Italy
Posts: 36

Posted: 12:45am 02 Oct 2016

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Dough,

shame on me !
You are right, if I read the bits backward the values are correct.
It is only necessary to write a boring function to use the bit sequence in the correct order.

Thank you a lot.

Pietro

twofingers

Guru

Joined: 02/06/2014
Location: Germany
Posts: 1573

Posted: 01:27am 02 Oct 2016

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Cremo said You are right, if I read the bits backward the values are correct.
It is only necessary to write a boring function to use the bit sequence in the correct order.

bitreverse

causality ≠ correlation ≠ coincidence

Cremo
Newbie

Joined: 21/07/2015
Location: Italy
Posts: 36

Posted: 04:04am 02 Oct 2016

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Hi twofingers, thank you.
Pietro

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