File Coverage

blib/lib/PINE64/MCP300x.pm

Criterion	Covered	Total	%
statement	9	59	15.2
branch	0	12	0.0
condition	0	9	0.0
subroutine	3	5	60.0
pod	2	2	100.0
total	14	87	16.0

#!/usr/bin/perl
use strict;
use Time::HiRes qw(usleep);
use PINE64::GPIO;

package PINE64::MCP300x;

our $VERSION = '0.91';

=pod
bit-banged SPI driver implementing
routines for MCP300x 4 or 8-channel
10-bit analog to digital converter
=cut

#SPI / bitbang varables
my ($clk, $din, $dout, $chpsel);

#channels: first bit is set to single, not differential
#5 bits because the first is the start bit
my @ch0 = (1,1,0,0,0);
my @ch1 = (1,1,0,0,1);
my @ch2 = (1,1,0,1,0);
my @ch3 = (1,1,0,1,1);
my @ch4 = (1,1,1,0,0);
my @ch5 = (1,1,1,0,1);
my @ch6 = (1,1,1,1,0);
my @ch7 = (1,1,1,1,1);

#instantiate PINE64 gpio device
my $p64 = PINE64::GPIO->new();

sub new{
	my $class = shift;
	my $self = bless {}, $class;

	#
	$clk = $_[0];		#clock
	$din = $_[1];		#instructions to adc
	$dout = $_[2];		#10-bit output from adc
	$chpsel = $_[3];	#latch / load to init comm to adc

	#init gpio lines
	$p64->gpio_enable($clk, 'out');
	$p64->gpio_enable($din, 'out');
	$p64->gpio_enable($dout, 'in');
	$p64->gpio_enable($chpsel, 'out');

	#init chpsel high, comm begins when
	#chipsel goes from high to low
	$p64->gpio_write($chpsel, 1);

	return $self;

}#end new

sub read300x{
	#init empty array that will
	#contain 10-bit reading from ADC
	my @reading = ();
	#get reading from the MCP3004 ADC
	#starts comm when cs goes from high to low

	#ADC channel number
	#channel is an array reference
	my $channel = $_[1];

	#delay between clock pulses
	#needs to operate at 10KHz so
	#sample is accurate, so min usleep(100)
	my $delay = $_[2];

	#reference voltate, used only for calculations
	#can be omitted
	my $vref = $_[3];

	#main clock variable
	my $i=0;

	#high flag for data gpio line
	my $hf = 0;

	#number of clock pulses,
	my $ncp = 34; #for 18 clock pulses

	#high or low state of clock pulse
	my $state = 0;
	my $seed = 3; #seed used to determine high or low, start 3 so first pulse is high

	#toggles CS line to init communication with the adc
	#start low, go high, then low.  comm begins when CS
	#brought from high to low
	$p64->gpio_write($chpsel, 0);
	Time::HiRes::usleep($delay);

	#main loop
	while($i<$ncp){
		$state = $seed%2;#toggles between 1 and 0
		$seed++;

		#clock pulse high
		if(($i%2) eq 0){
			#print "i: $i\tcp high\tstate: $state\n";

			if($channel->[$i/2] eq 1 && $i <=8){
				$p64->gpio_write($din, 1);
				$hf = 1;#set high flag
				#print "ch[".($i/2)."]: ".$channel->[$i/2]."\n";
			}#end if
			if($channel->[$i/2] eq 0 && $i <=8){
				$p64->gpio_write($din,0);
			}#end if zero on data line
		}#end if high

		#if($i>8){#data line
			#everything after D0 bit is don't care,
			#set to state
			#gpio_write($din, $state);
		#}#end else

		#clock pulse
		$p64->gpio_write($clk, $state);

		#read data out
		#data clocked out on falling
		#edge of clk
		if(($i%2) == 1 && $i >12){
			#read state of gpio pin connected
			#to data out of ADC
			push @reading, $p64->gpio_read($dout);
			#print "i[$i]: ".$reading[($i-14)/2]."\n"
		}#end read data out

		#lower data if high flag set
		if($hf eq 1){
			#gpio_write($din,0);
			$hf = 0;#reset high flag
		}#end if

		#pause between clk pls
		Time::HiRes::usleep($delay);

		#increment counter
		$i++;
	}#end while

	#make din low
	$p64->gpio_write($din, 0);

	#make chip select high
	$p64->gpio_write($chpsel, 1);

	#perform calcuations, return a voltage
	#based of 10-bit reading, and vref val
	my $bindig = 512;
	my $rdgval = 0;
	my $voltage = 0;
	for(my $x; $x<10;$x++){
		if($reading[$x] == 1){
			$rdgval = $rdgval + $bindig;
		}#end if
		$bindig = $bindig / 2;
	}#end for

	#voltage calculation
	$voltage = ($rdgval*$vref)/1024;

	return (\@reading, $rdgval, $voltage);
}#end read3004

1;
__END__