CE204022 - PSoC® 4 IDAC7 Sawtooth Waveform Generator Objective This code example shows the user the basics of using the IDAC7 found in some PSoC® 4 devices. A simple sawtooth or voltage ramp waveform is generated using the IDAC7 current Digital to Analog converter. Overview This code example generates a linear voltage ramp (sawtooth) waveform by incrementing the current DAC’s output until the maximum value, it then starts back at zero. Since the IDAC7 is a current DAC, an external load resistor is used to generate a voltage from the current source. Requirements Tool: PSoC Creator 3.3 SP2 or higher Programming Language: C (GCC 4.9.0) or higher Associated Parts: PSoC 4000S, PSoC 4100S and PSoC Analog Coprocessor Related Hardware: CY8CKIT-041-40XX, CY8CKIT-041-41XX and CY8CKIT-048 Design This simple design demonstrates how to create a voltage waveform from a current source. The IDAC is used to source a current through an external resistor connected to Vss, See Figure 1 below. The waveform is seen across the resistor between Vss and Vout. The internal IDAC7 is connected to GPIO port P0[7]. The Load Resistor is connected between P0[7] and Vss as shown in Figure 1. Figure 1 Voltage Ramp Generator Schematic www.cypress.com Document No. 002-04022 Rev.** 1 PSoC® 4 IDAC7 Sawtooth Waveform Generator Design Considerations With the 3.3K load resistor and using the highest current range (600 uA), the voltage swing will be between 0 and 2Vpp. Use ohms law to calculate the voltage range that is required for a specific project. The load resistor was selected to generate a 2 volt peak-to-peak signal using the highest current range. The load resistor is calculated using ohms law R = V/I, see Equation 1 below. Equation 1 RLoad = ଶ ୳ = 3.3 ܱ ܭℎ݉ ݏ By either changing the load resistor and/or selecting one of 6 current ranges, any voltage range between the supply rails can be achieved. Additionally a waveform may be referenced to Vdda instead of Vss by changing the Polarity to “Negative (Sink)” and connecting the load resistor to Vdda instead of Vss. The IDAC’s range and polarity may also be changed during runtime with the IDAC7_1_SetRange() and IDAC7_1_SetPolarity() functions respectively. Hardware Setup For this code example a 3.3K resistor needs to be connected from Port P0[7] to Vss as shown in Figure 1. Connect an oscilloscope across the resistor to observe the waveform. Components Table 1 lists the PSoC Creator Components used in this example, as well as the hardware resources used by each. Table 1. List of PSoC Creator Components Component or User Module Version Hardware Resources IDAC7_1 1.0 Capsense block Iout 2.20 GPIO ( P0[7] ) Resistor 1.0 External Components Parameter Settings The IDAC7 component has three parameters, Polarity, Range, and Value. For this example, the Polarity should be set to “Positive (Source)” and the Range to “0-609.6 uA”. The Value does not matter since it will be changed during runtime in the code. Figure 2 IDAC7 user interface www.cypress.com Document No. 002-04022 Rev.** 2 PSoC® 4 IDAC7 Sawtooth Waveform Generator Operation 1) Attach 3.3K load resistor between port P0[7] and Vss. 2) Attach scope probe across load resistor. 3) Observe a 2 volt peak-to-peak sawtooth waveform on oscilloscope. Related Documents Table 2 lists all relevant application notes, code examples, knowledge base articles, device datasheets, and Component datasheets. Table 2. Related Documents Application Notes AN211293 Getting Started with PSoC® Analog Coprocessor PSoC Creator Component Datasheets IDAC7 IDAC7 Datasheet Pins General Purpose IO Pins Device Documentation CY8C4Axx Datasheet PSoC® Analog Coprocessor: CY8C4Axx Family Datasheet CY8C4200 Datasheet PSoC® 4200 Programmable Digital CY8C4200M Datasheet PSoC® 4: PSoC 4200M Family Datasheet Development Kit (DVK) Documentation CY8CKIT-048 PSoC® Analog Coprocessor Pioneer Kit CY8CKIT-042 PSoC® Pioneer Kit CY8CKIT-044 PSoC® Pioneer Kit PSoC® Family Web Page PSoC® Analog Coprocessor 32-bit ARM® Cortex®-M0 PSoC® 4200 Programmable Digital www.cypress.com Document No. 002-04022 Rev.** 3 PSoC® 4 IDAC7 Sawtooth Waveform Generator Document History Document Title: CE204022 - PSoC® 4 IDAC7 Sawtooth Waveform Generator Document Number: 002-04022 Revision ** ECN 5265164 www.cypress.com Orig. of Change MEH Submission Date 1/22/2016 Description of Change New Code Example Document No. 002-04022 Rev.** 4 PSoC® 4 IDAC7 Sawtooth Waveform Generator Worldwide Sales and Design Support Cypress maintains a worldwide network of offices, solution centers, manufacturer’s representatives, and distributors. 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