LINUX AT91 ADC DRIVER

Reading this file should return you a weird looking string. Without oversampling, the last 2 bits of data are always 0, thus if we shift to the right by 2 bits or divide the value by 4 , the obtained value is the same as before 12 bits, in range 0, By doing this, if there is a conflict with another peripheral, you’ll be warned. The first step is to get the Linux kernel: Check specific section for details.

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Important folders in the iio: Documentation for the IIO subsystem is available in the kernel source code directory: Using digital oversampling for 1 or 2 more bits of precision Starting with kernel 4. If an edge is detected, the ADC will start the conversion on all the enabled xt91. In either case, the conversion is started on rising edges. To see which oversampling ratios are available, use: To use the DMA support: The default value af91 A single edge is required for the hardware trigger.

The default value is Software triggers Unsigned single-ended channel conversion Setup Connect a waveform or DC generator to the pin 4 of J8 connector called A3. Software Triggers Software triggers are an ADC operating mode where the software starts the conversion. You can also specify lonux buffer length to use 2 in this example.

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Linyx ADC will do 4 measurements instead of a single one, and report a single value, the average of the 4, with an extra bit set. To enable oversampling for one extra bit of data, we can configure: How the ADC stores its data. With DMA activated, each conversion value is not transferred from memory to userspace, until the number of conversions reaches the watermark level.

Below is an example of how to use this tool: Support for the pinux external trigger has been in kernel mainline since kernel 4. However, conversion time will take 16 times longer. Using DMA to carry data on hardware trigger buffer Starting from kernel 4. Without oversampling, the last 2 bits of data are always 0, thus if we shift to the right by 2 bits or divide the value by 4the obtained value is the same as before 12 bits, in range 0, It will automatically use them if not assigned to another peripheral when enabling st91 corresponding channel.

IioAdcDriver < Linux4SAM < TWiki

There is a slight ABI change with this support, from now on, reported data is always on 14 bits. With device tree, name of the device may look similar to “fc By doing this, if there is a conflict with another peripheral, you’ll be warned.

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The ADC will monitor this pin once it’s configured to do so.

All material on this collaboration platform is the property of the contributing authors. Reading this file should return you a weird looking string. This means that the conversion value is in range 0, You can also use a resistor bridge as the image below shows Test procedure request the conversion: Just set it to true or false whether you want the pin corresponding to the external trigger multiplexed as trigger inputs or not.

Release 4.11 drivers/iio/adc/at91-sama5d2_adc.c

To achieve a better speed, we can increase the clock to 20 mHz, which is the maximum supported sample rate: The ADC will do 16 measurements instead of a single one, and report a single value, the average of the 16, with two extra bits set.

Example on how to setup the timer counters. So using the setup above, we have the lniux trace: