MCP48x2 DAC SPI library

Quick start

1. Add submodule to your project

git submodule add git@github.com:anisyanka/mcp48x2.git /third/party/folder

2. Add definition for a DAC type and sources

# C defines
C_DEFS += -DDAC_TYPE_MCP4822
C_SOURCES += /third/party/folder/mcp48x2.c
C_INCLUDES += /third/party/folder

For now DAC_TYPE_MCP4822 (12 bit DAC), DAC_TYPE_MCP4812 (10 bit DAC) and DAC_TYPE_MCP4802 (8 bit DAC) are only supported.

3. Call default initialization function

mcp48x2_ret_t mcp48x2_default_init(mcp48x2_device_t *dev, mcp48x2_ll_t *ll);

Default setup is:

• both channels are in active mode
• gain factor equals 2 for both channels
• initial output voltages are set to zero for both channels.

You can use other init function from the header file if the default setup doesn't fit you.

dev - describes one instance of your DACs on your board. The board can contain plenty of DACs. This param helps you to control each instance separately.

ll - describes low level functions to allow the library to control hardware. In this case to control GPIOs and SPI. It looks like this:

typedef struct
{
	/* Manage NSS pin */
	void (*nss_set)(void);
	void (*nss_reset)(void);

	/* Manage LDAC pin */
	void (*ldac_set)(void);
	void (*ldac_reset)(void);
	void (*delay_us)(uint32_t us);

	/* Transmit 16 bits with SPI */
	mcp48x2_ret_t (*spi_write_packet)(uint16_t data);
} mcp48x2_ll_t;

You have to implement all these function by yourself and pass it to the library. The lib is able to work on different hardwares with the help of this.

4. Enjoy using the DAC

Set output voltage with the help of:

mcp48x2_ret_t mcp48x2_set_channel_value(mcp48x2_device_t *dev,
                                        mcp48x2_ch_t ch, uint16_t val);

Remember that:

Vout = (2048 * val * G) / 2^(DAC resolution)

• 2048 - internal reference voltage
• G - gain factor
• val = [0 - 4095] for MCP4922
• val = [0 - 1023] for MCP4912
• val = [0 - 255] for MCP4902