UM0851 datasheet(188/245 Pages) STMICROELECTRONICS

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Human interface device (HID) drivers

UM0851

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Doc ID 16604 Rev 2

Kernel level:

spear_adc_chan_configure(dev, &chan_config);

On success zero is returned otherwise negative standard kernel errors are returned.

In the function calls, chan_config is an instance of struct adc_chan_config:

struct adc_chan_config {

enum adc_chan_id chan_id; /* channel to be configured */

enum adc_avg_samples avg_samples; /* number of average samples */

unsigned int scan_rate; /* rate at which ADC converts data, in

microseconds

int scan_rate_fixed; /* if 1 configured scan rate should be

equal to requested can rate, else if 0

configured scan rate can be less than equal

to requested scan rate.*/

};

The above functions configure an ADC channel if the ADC device is already configured.

They also initiate the conversion. In SINGLE_CONVERSION mode the channel must be

configured before each conversion. In CONTINUOUS_CONVERSION mode, the ADC

channel is configured only once and then multiple read commands may follow.

The scan rate is common to all ADC channels. So changing the scan rate affects all ADC

channels. In non-DMA mode, the scan rate is configured to the minimum scan rate

requested and already configured by the channel configurations.

In DMA mode:

●

If DMA is requested and the scan rate of the DMA is lower than the already configured

scan rate, then the scan rate is configured.

●

Otherwise an error is returned.

If DMA is already configured and a new non-DMA request is made:

●

If the requested scan rate is less than already configured scan rate then an error is

returned

●

Otherwise the scan rate is not changed and success is returned.

This function returns zero on success and -1 on error and errno is set appropriately.

Read converted data

After configuring the ADC channel, you can read the converted voltage on the ADC channel.

The output data is in millivolts.

The converted data can be read using the following calls:

User level:

read(fd, &data, count);

On success, it returns the number of bytes copied otherwise -1 is returned and errno is set

appropriately.

Kernel level:

spear_adc_get_data(dev, ADC_CHANNEL0, &data, count);

/* Data: is variable in which converted voltage in millivolts will

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