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Incorrect analog input read from pins A1 to A5

Created by: bamsbamx at: 5/3/2017 7:18 PM (6 Replies)

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5/3/2017 7:18 PM	Rate (0)
bamsbamx Posts: 9 Rating: (1)	Hi, I am trying to read the analog input for the pins A1 to A5 of the Arduino expansion board. All the time I try to read any input for these pins it returns the value corresponding to pin A0. #include <iostream> #include "mraa.hpp" #include <TinkerKit2.h> #include <unistd.h> int main(void) { std::cout << mraa::getVersion() << std::endl; mraa::Aio * a0 = new mraa::Aio(0); mraa::Aio * a5 = new mraa::Aio(5); if (a0 == NULL \|\| a5 == NULL) { return MRAA_ERROR_UNSPECIFIED; } uint16_t adc_value_0, adc_value_5; for (;;) { adc_value_0 = a0->read(); adc_value_5 = a5->read(); fprintf(stdout, "ADC A0=%d A5=%d\n", adc_value_0, adc_value_5); } return 0; } For this test, I attached the potentiometer middle pin only to the A0 pin, just like in the attached image (it corresponds to the Arduino board, but you get the point). However, fprintf shows the same values for A0 and A5, and it happens the same for A1, A2, A3, and A4 pins The mraa version installed is : root@gcis-iot2040:~# opkg info libmraa0 Package: libmraa0 Version: 0.6.2 Provides: libmraa-dev, libmraa-dbg, libmraa-doc Replaces: libmraa-dev, libmraa-dbg, libmraa-doc Conflicts: libmraa-dev, libmraa-dbg, libmraa-doc Status: unknown ok not-installed Section: libs Architecture: i586 Maintainer: Intel IoT-Devkit MD5Sum: 77c7285bd95f774b2b3b560a4480ad0f Size: 266598 Filename: libmraa0_0.6.2_i586.ipk Source: https://github.com/intel-iot-devkit/mraa Description: mraa built using CMake Package: libmraa0 Version: 0.10.1-r0 Depends: python-core, libc6 (>= 2.23) Provides: mraa Status: install user installed Architecture: i586-nlp-32 Installed-Time: 1477641019 Is this a hardware problem? Any way to fix it? Attachment AnalogReadSerial_BB.png (378 Downloads)
bamsbamx Posts: 9 Rating: (1)
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5/3/2017 7:48 PM	Rate (0)
jan-k Silver Member Joined: 4/28/2015 Last visit: 6/28/2024 Posts: 578 Rating: (43)	Do you have /sys/bus/iio/devices/iio:device0/? What do you get from in_voltage0_raw to in_voltage5_raw in that folder? Those five correspond to A0 to A5.

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5/3/2017 8:26 PM	Rate (0)
bamsbamx Posts: 9 Rating: (1)	jan-k Do you have /sys/bus/iio/devices/iio:device0/? What do you get from in_voltage0_raw to in_voltage5_raw in that folder? Those five correspond to A0 to A5. These are the values I get: root@gcis-iot2040:/sys/bus/iio/devices/iio:device0# cat in_voltage0_raw 2780 root@gcis-iot2040:/sys/bus/iio/devices/iio:device0# cat in_voltage1_raw 864 root@gcis-iot2040:/sys/bus/iio/devices/iio:device0# cat in_voltage2_raw 916 root@gcis-iot2040:/sys/bus/iio/devices/iio:device0# cat in_voltage3_raw 880 root@gcis-iot2040:/sys/bus/iio/devices/iio:device0# cat in_voltage4_raw 3712 root@gcis-iot2040:/sys/bus/iio/devices/iio:device0# cat in_voltage5_raw 3644 It seems <in_voltagei_raw> is the same for (i=1, i=2, i=3). However, there is a small variation between them in_voltage0_rawseems to be 0 to 4092 (depending on potentiometer value) in_voltage1_raw,in_voltage2_raw,in_voltage3_rawlook like they are in the same range (388? to 1088?) (depending on potentiometer value) Must be because they are not connected to ground in_voltage4_raw, in_voltage5_rawkeep between 3500 and 3800 (do NOT depend on potentiometer value TO SUM UP: in_voltage_raw returns the correct value (except for A4 and A5) while mraa::Aio::read() returns the value of A0 for all pin readings
bamsbamx Posts: 9 Rating: (1)	Last edited by: bamsbamx at: 5/3/2017 8:38:45 PM Last edited by: bamsbamx at: 5/3/2017 8:39:20 PM Last edited by: bamsbamx at: 5/3/2017 8:40:18 PM
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5/3/2017 8:42 PM	Rate (0)
jan-k Silver Member Joined: 4/28/2015 Last visit: 6/28/2024 Posts: 578 Rating: (43)	A0 -> in_voltage0_raw (* in_voltage0_scale = voltage in mV), provided the potentiometer is attached to A0. Can you confirm that? Now, if you connect the potentiometer to A1..A5, do you get similar results for each of them? Ignore reported values for floating pins (unconnected). Those act more like antennas at that point. If that is all true, we have an issue with mraa and how it interprets the inputs from that ADC device. I'll try that out myself as well (currently no device in physical reach).

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5/3/2017 8:46 PM	Rate (0)
bamsbamx Posts: 9 Rating: (1)	jan-k A0 -> in_voltage0_raw (* in_voltage0_scale = voltage in mV), provided the potentiometer is attached to A0. Can you confirm that? Now, if you connect the potentiometer to A1..A5, do you get similar results for each of them? Ignore reported values for floating pins (unconnected). Those act more like antennas at that point. If that is all true, we have an issue with mraa and how it interprets the inputs from that ADC device. I'll try that out myself as well (currently no device in physical reach). Yes, all readings from in_voltage0_raw to in_voltage3_raw are correct. So the conclusion is there might be a problem with mraa. Maybe changing the installed mraa version could fix the problem?
bamsbamx Posts: 9 Rating: (1)	Last edited by: bamsbamx at: 5/4/2017 11:03:22 AM
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5/4/2017 11:04 AM	Rate (1)
jan-k Silver Member Joined: 4/28/2015 Last visit: 6/28/2024 Posts: 578 Rating: (43)	Yes, you should use mraa from the latest example image (or via your own yocto build of meta-iot2000). That Intel opkg repo is outdated, specifically /wrt mraa.

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5/4/2017 3:22 PM	Rate (0)
bamsbamx Posts: 9 Rating: (1)	jan-k Yes, you should use mraa from the latest example image (or via your own yocto build of meta-iot2000). That Intel opkg repo is outdated, specifically /wrt mraa. Finallly! It seems that the installed image version was 2.1.1 according to cat /etc/image-release So updating the image version to 2.1.3 provided here https://support.industry.siemens.com/cs/document/109741799/simatic-iot2000-sd-card-example-image?dti=0&lc=en-WW fixed the problem for all analog inputs (from A0 to A5)
bamsbamx Posts: 9 Rating: (1)
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