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How to connect Raspberry Pi to ADC MCP 3008 using new SPI Simulink blocks?

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I want to interface a RaspberryPi with an ADC MCP3008 using Simulink, in particular using the new block "SPI Register Read" available in the latest Simulink version (without writing C code or Matlab code). In this block is required a Register Address where SPI has to read the value from the slave. I don't know how to find it because I'm not sure if it's a MCP3008 register or it's an address always used from RPi to communicate with all the slaves. Can anyone help me?

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Accepted Answer

Sharan Paramasivam Murugesan
SPI Register read/write blocks are meant for memory devices such as EEPROM.
So in your case, following the example,
try using "SPI Master Transfer" block with a constant block having value [1, bin2dec('10000000'), 0] as input. Here in the binary value '10000000', the first 4 bits '1000' represents single-ended voltage measurement at CH0 is requested (refer to the datasheet for more info). To read from CH1, then '1001' should be used. To retrieve the voltage value from the output, say 'data', you have to model the logic mentioned in the above doc (also mentioned below) using Simulink blocks.
highbits = bitand(data(2), bin2dec('11'));
voltage = double(bitor(bitshift(highbits, 8), data(3)));
voltage = (3.3/1024) * voltage;

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Grissa Mohamed Amine
Grissa Mohamed Amine on 6 Jan 2018
i did the same thing with mcp3208 and i customize the code but it does not work, do you have another Solution please ?

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More Answers (3)

Bikash Sah
Bikash Sah on 10 Jul 2018
Hai Sharan, can you please explain the use of a constant block having value [1, bin2dec('10000000'), 0] as input to SPI Master Transfer. You wrote about the first four numeric values to control bits; what about the other four? What does the value "1" and "0" corresponds to. Also, a better explanation to understand the following code would be a great help.
clear mcp3008
mcp3008 = spidev(rpi, 'CE0');
data = uint16(writeRead(mcp3008,[1, bin2dec('10000000'), 0]));
highbits = bitand(data(2), bin2dec('11'));
voltage = double(bitor(bitshift(highbits, 8), data(3)));
voltage = (3.3/1024) * voltage;

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Johannes Börner
Johannes Börner on 31 Jul 2018
Hi, Im currently trying to read the data of an MCP3008 in the way described above. Though I can manage the readings from command line, I have no indication that the SPI Master Transfer is working in any way when running the model. Is there any Simulink example using this block? Did anyone recently manage to get readings from an MCP3008?
Kind regards

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Kiyo Akabori
Kiyo Akabori on 7 Nov 2019
For me, placing a Data Type Conversion block of uint8 between the constant block of [1, bin2dec('10000000'), 0] and SPI Master Transfer block did the trick. Without the conversion block, an array of type double was fed to the SPI master block, which ended up outputing values very close to zero (about 1e-300).

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Abdo Be
Abdo Be on 18 Jun 2019
Hi, After multiple trials to read data from MCP3008 using SPI read block, it finally works for the first analog input (CH0),
However, in order to read analog input from the other channels (CH1,..CH7), normally the SPI write block should be driven by a constant block, I want to know the source of this synthax "[1, bin2dec('10000000'), 0]" that Sharan Paramasivam Murugesan mentionned above, because when I tested this block it doesn't change the analog input.

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MOKHLIS MOHCINE
MOKHLIS MOHCINE on 31 Jul 2019
Hello Abdo Be, I did the same steps you said, but they didn't work. Can you please share with us the simulink file that you're used. It will be very helpfull. Thanks in advance.

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