DAC.zip_DAC

/*********************************************************************** * $Id$ abstract.txt 2011-06-02 * @file DAC\Dac_SineWave\abstract.txt * @brief Description of the example to generate a sinewave signal by DAC. * @version 1.0 * @date 02. June. 2011 * @author NXP MCU SW Application Team * * Copyright(C) 2011, NXP Semiconductor * All rights reserved. * *********************************************************************** * Software that is described herein is for illustrative purposes only * which provides customers with programming information regarding the * products. This software is supplied "AS IS" without any warranties. * NXP Semiconductors assumes no responsibility or liability for the * use of the software, conveys no license or title under any patent, * copyright, or mask work right to the product. NXP Semiconductors * reserves the right to make changes in the software without * notification. NXP Semiconductors also make no representation or * warranty that such application will be suitable for the specified * use without further testing or modification. **********************************************************************/ @Example description: Purpose: This example describes how to use DMA to generate a sinewave signal Process: DAC will be initialized with maximum current is 700uA. This allows a maximum update rate of 1Mhz Formula for ouput voltage on AOUT is: AOUT = VALUE x ((Vrefp - Vrefn)/1024)+Vrefn in which: - Vrefp: tied to VDD(3.3V) - Vrefn: tied to Vss DAC will generate a sinewave with peak to peak is within Vrefp and Vrefn. We need to prepare a look up table with 60 items, each item is the value to update AOUT voltage, and it's correspondent to a sample point of 1 circle sinewave signal. The formula is below: for(i=0;i<NUM_SINE_SAMPLE;i++) //NUM_SINE_SAMPLE = 60 { dac_sine_lut[i] = 512 + 512*sin(i); dac_sine_lut[i] = (dac_sine_lut[i]<<6); } GPDMA channel 0 is configured in this example and used to transfer dac_sine_lut[i] to DAC peripheral. When the last item of dac_sine_lut is transfered, GPDMA will roll back to transfer the first item. DAC is configured to use time out for each DAC value update and trigger GPDMA to fill DAC value register. This time out value can also be used to calculate the sinewave frequency: time out = (PCLK_DAC_IN_MHZ*1000000)/(SINE_FREQ_IN_HZ*NUM_SINE_SAMPLE); Where: - SINE_FREQ_IN_HZ = 60 - NUM_SINE_SAMPLE = 60 Observe AOUT(P0.26) signal by oscilloscope. @Directory contents: \Keil: includes RVMDK (Keil)project and configuration files \EWARM: includes EWARM (IAR) project and configuration files Dac_SineWave.c: Main program @How to run: Hardware configuration: This example was tested on: 1. LPC1788 OEM Board rev A and OEM Base Board rev A 2. LPC1788 IAR Start Kit Rev.B - 3.3VA_E :ON - VREG :ON - IO_E :ON - PWR_SEL :depends on power source selection (Choose correct working board by setting "_CURR_USING_BRD" marco in .\BoardSupport\bsp.h file) DAC_OUT (AOUT-P0.26) pin: 1. LPC1788 OEM Board rev A and OEM Base Board rev A + J3.28 2. LPC1788 IAR Start Kit Rev.B + EXT-11 Serial display configuration: (e.g: TeraTerm, Hyperterminal, Flash Magic...) 1. LPC1788 OEM Board rev A and OEM Base Board rev A - UART0: USB serial port + All jumpers: Default - UART1: + P0.15 (@ J5.19) - JP12.2 + P0.16 (@ J3.24) - JP13.2 - UART2: + JP6: 1-2: OFF 3-4: OFF 5-6: ON + JP12: 1-2 + JP13: 1-2 + Other jumpers: Default - UART3: + P0.2 (@J5.13) - JP12.2 + P0.3 (@J5.14) - JP13.2 - UART4: + P0.22 (@J3.25) - JP12.2 + P2.9 (@J3.15) - JP13.2 2. LPC1788 IAR Start Kit Rev.B - UART0: All jumpers: optional Note: Pls sure that "USED_UART_DEBUG_PORT" macro in debug_frmwrk.h is set correctly Setting: + 115200bps + 8 data bit + No parity + 1 stop bit + No flow control Running mode: This example can run on RAM/ROM mode. Note: If want to burn hex file to board by using Flash Magic, these jumpers need to be connected: 1. LPC1788 OEM Board rev A and OEM Base Board rev A - JP20: 1-2: ON 3-4: ON (Using UART0 on USB serial port Sure that you choose correct COM port number - Pls reference at: "Device Manager" -> "Ports(COM & LPT)" -> "USB Serial Port (COMx)") 2. LPC1788 IAR Start Kit Rev.B - RST_E: ON - ISP_E: ON Step to run: - Step 1: Build example. - Step 2: Burn hex file into board (if run on ROM mode) - Step 3: Configure hardware as above instruction - Step 4: Run example and observe AOUT(P0.26) signal by oscilloscope