1 /*
2 * Copyright (c) 2021 Laird Connectivity
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6 #define DT_DRV_COMPAT microchip_mcp4725
7
8 #include <zephyr/kernel.h>
9 #include <zephyr/drivers/i2c.h>
10 #include <zephyr/drivers/dac.h>
11 #include <zephyr/logging/log.h>
12
13 LOG_MODULE_REGISTER(dac_mcp4725, CONFIG_DAC_LOG_LEVEL);
14
15 /* Information in this file comes from MCP4725 datasheet revision D
16 * found at https://ww1.microchip.com/downloads/en/DeviceDoc/22039d.pdf
17 */
18
19 /* Defines for field values in MCP4725 DAC register */
20 #define MCP4725_DAC_MAX_VAL 0xFFF
21
22 #define MCP4725_FAST_MODE_POWER_DOWN_POS 4U
23 #define MCP4725_FAST_MODE_DAC_UPPER_VAL_POS 8U
24 #define MCP4725_FAST_MODE_DAC_UPPER_VAL_MASK 0xF
25 #define MCP4725_FAST_MODE_DAC_LOWER_VAL_MASK 0xFF
26
27 #define MCP4725_READ_RDY_POS 7U
28 #define MCP4725_READ_RDY_MASK (0x1 << MCP4725_READ_RDY_POS)
29
30 /* After writing eeprom, the MCP4725 can be in a busy state for 25 - 50ms
31 * See section 1.0 of MCP4725 datasheet, 'Electrical Characteristics'
32 */
33 #define MCP4725_BUSY_TIMEOUT_MS 60U
34
35 struct mcp4725_config {
36 struct i2c_dt_spec i2c;
37 };
38
39 /* Read mcp4725 and check RDY status bit */
mcp4725_wait_until_ready(const struct device * dev)40 static int mcp4725_wait_until_ready(const struct device *dev)
41 {
42 const struct mcp4725_config *config = dev->config;
43 uint8_t rx_data[5];
44 bool mcp4725_ready = false;
45 int ret;
46 int32_t timeout = k_uptime_get_32() + MCP4725_BUSY_TIMEOUT_MS;
47
48 /* Wait until RDY bit is set or return error if timer exceeds MCP4725_BUSY_TIMEOUT_MS */
49 while (!mcp4725_ready) {
50 ret = i2c_read_dt(&config->i2c, rx_data, sizeof(rx_data));
51
52 if (ret == 0) {
53 mcp4725_ready = rx_data[0] & MCP4725_READ_RDY_MASK;
54 } else {
55 /* I2C error */
56 return ret;
57 }
58
59 if (k_uptime_get_32() > timeout) {
60 return -ETIMEDOUT;
61 }
62 }
63
64 return 0;
65 }
66
67 /* MCP4725 is a single channel 12 bit DAC */
mcp4725_channel_setup(const struct device * dev,const struct dac_channel_cfg * channel_cfg)68 static int mcp4725_channel_setup(const struct device *dev,
69 const struct dac_channel_cfg *channel_cfg)
70 {
71 if (channel_cfg->channel_id != 0) {
72 return -EINVAL;
73 }
74
75 if (channel_cfg->resolution != 12) {
76 return -ENOTSUP;
77 }
78
79 return 0;
80 }
81
mcp4725_write_value(const struct device * dev,uint8_t channel,uint32_t value)82 static int mcp4725_write_value(const struct device *dev, uint8_t channel,
83 uint32_t value)
84 {
85 const struct mcp4725_config *config = dev->config;
86 uint8_t tx_data[2];
87 int ret;
88
89 if (channel != 0) {
90 return -EINVAL;
91 }
92
93 /* Check value isn't over 12 bits */
94 if (value > MCP4725_DAC_MAX_VAL) {
95 return -ENOTSUP;
96 }
97
98 /* WRITE_MODE_FAST message format (2 bytes):
99 *
100 * || 15 14 | 13 12 | 11 10 9 8 || 7 6 5 4 3 2 1 0 ||
101 * || Fast mode (0) | Power-down bits (0) | DAC value[11:8] || DAC value[7:0] ||
102 */
103 tx_data[0] = ((value >> MCP4725_FAST_MODE_DAC_UPPER_VAL_POS) &
104 MCP4725_FAST_MODE_DAC_UPPER_VAL_MASK);
105 tx_data[1] = (value & MCP4725_FAST_MODE_DAC_LOWER_VAL_MASK);
106 ret = i2c_write_dt(&config->i2c, tx_data, sizeof(tx_data));
107
108 return ret;
109 }
110
dac_mcp4725_init(const struct device * dev)111 static int dac_mcp4725_init(const struct device *dev)
112 {
113 const struct mcp4725_config *config = dev->config;
114
115 if (!device_is_ready(config->i2c.bus)) {
116 LOG_ERR("I2C device not found");
117 return -EINVAL;
118 }
119
120 /* Check we can read a 'RDY' bit from this device */
121 if (mcp4725_wait_until_ready(dev)) {
122 return -EBUSY;
123 }
124
125 return 0;
126 }
127
128 static const struct dac_driver_api mcp4725_driver_api = {
129 .channel_setup = mcp4725_channel_setup,
130 .write_value = mcp4725_write_value,
131 };
132
133
134 #define INST_DT_MCP4725(index) \
135 static const struct mcp4725_config mcp4725_config_##index = { \
136 .i2c = I2C_DT_SPEC_INST_GET(index), \
137 }; \
138 \
139 DEVICE_DT_INST_DEFINE(index, dac_mcp4725_init, \
140 NULL, \
141 NULL, \
142 &mcp4725_config_##index, POST_KERNEL, \
143 CONFIG_DAC_MCP4725_INIT_PRIORITY, \
144 &mcp4725_driver_api);
145
146 DT_INST_FOREACH_STATUS_OKAY(INST_DT_MCP4725);
147
