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[/] [open8_urisc/] [trunk/] [VHDL/] [o8_pwm_adc.vhd] - Rev 331
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-- Copyright (c)2020 Jeremy Seth Henry -- All rights reserved. -- -- Redistribution and use in source and binary forms, with or without -- modification, are permitted provided that the following conditions are met: -- * Redistributions of source code must retain the above copyright -- notice, this list of conditions and the following disclaimer. -- * Redistributions in binary form must reproduce the above copyright -- notice, this list of conditions and the following disclaimer in the -- documentation and/or other materials provided with the distribution, -- where applicable (as part of a user interface, debugging port, etc.) -- -- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY -- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED -- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE -- DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY -- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES -- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; -- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND -- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT -- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS -- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -- -- VHDL Entity: pwm_adc -- Description: Integrates a PWM input to return the approximate duty cycle -- Uses a 1kB block ram as storage for a rolling integrator that -- acts as a simple successive-approximation ADC. -- -- Revision History -- Author Date Change ------------------ -------- --------------------------------------------------- -- Seth Henry 05/07/20 Design Start library ieee; use ieee.std_logic_1164.all; use ieee.std_logic_unsigned.all; library work; use work.open8_pkg.all; entity o8_pwm_adc is generic( Address : ADDRESS_TYPE ); port( Open8_Bus : in OPEN8_BUS_TYPE; Rd_Data : out DATA_TYPE; -- PWM_In : in std_logic ); end entity; architecture behave of o8_pwm_adc is alias Clock is Open8_Bus.Clock; alias Reset is Open8_Bus.Reset; alias uSec_Tick is Open8_Bus.uSec_Tick; constant User_Addr : std_logic_vector(15 downto 0) := Address(15 downto 0); alias Comp_Addr is Open8_Bus.Address(15 downto 0); signal Addr_Match : std_logic := '0'; signal Rd_En_d : std_logic := '0'; signal Rd_En_q : std_logic := '0'; signal Sample : DATA_TYPE := x"00"; signal RAM_Addr : std_logic_vector(9 downto 0) := (others => '0'); signal RAM_Data : DATA_TYPE := x"00"; signal Accumulator : std_logic_vector(17 downto 0) := (others => '0'); signal Average : DATA_TYPE := x"00"; begin Addr_Match <= '1' when Comp_Addr = User_Addr else '0'; Rd_En_d <= Addr_Match and Open8_Bus.Rd_En; io_reg: process( Clock, Reset ) begin if( Reset = Reset_Level )then Rd_En_q <= '0'; Rd_Data <= OPEN8_NULLBUS; elsif( rising_edge( Clock ) )then Rd_En_q <= Rd_En_d; Rd_Data <= OPEN8_NULLBUS; if( Rd_En_q = '1' )then Rd_Data <= Average; end if; end if; end process; -- PWM input is binary, so the sample swings between 0x00 and 0xFF Sample <= (others => PWM_In); U_DP : entity work.o8_pwm_adc_ram port map( address => RAM_Addr, clock => Clock, data => Sample, wren => '1', q => RAM_Data ); ADC_proc: process( Clock, Reset ) begin if( Reset = Reset_Level )then RAM_Addr <= (others => '0'); Accumulator <= (others => '0'); Average <= (others => '0'); elsif( rising_edge(Clock) )then RAM_Addr <= RAM_Addr + 1; Accumulator <= Accumulator + ("0000000000" & RAM_Data); if( RAM_Addr = 0 )then Accumulator <= (others => '0'); Average <= Accumulator(17 downto 10); end if; end if; end process; end architecture;
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