Harald Welte | c3f170d | 2019-02-24 09:06:59 +0100 | [diff] [blame] | 1 | /* Bit-banging I2C layer, inspired to a large extent from Linux kernel |
| 2 | * i2c-algo-bit.c code (C) 1995-2000 Simon G. Vogl. This particular |
| 3 | * implementation is (C) 2019 by Harald Welte <laforge@gnumonks.org> |
| 4 | * |
| 5 | * SPDX-License-Identifier: GPL-2.0-or-later |
| 6 | */ |
| 7 | |
| 8 | #include <hal_gpio.h> |
| 9 | #include <hal_delay.h> |
| 10 | #include <err_codes.h> |
| 11 | #include "i2c_bitbang.h" |
| 12 | |
| 13 | #define setsda(adap, val) gpio_set_pin_level((adap)->pin_sda, val) |
| 14 | #define setscl(adap, val) gpio_set_pin_level((adap)->pin_scl, val) |
| 15 | |
| 16 | static int getsda(const struct i2c_adapter *adap) |
| 17 | { |
| 18 | int rc; |
| 19 | gpio_set_pin_direction(adap->pin_sda, GPIO_DIRECTION_IN); |
| 20 | rc = gpio_get_pin_level(adap->pin_sda); |
| 21 | gpio_set_pin_direction(adap->pin_sda, GPIO_DIRECTION_OUT); |
| 22 | return rc; |
| 23 | } |
| 24 | |
| 25 | static int getscl(const struct i2c_adapter *adap) |
| 26 | { |
| 27 | int rc; |
| 28 | gpio_set_pin_direction(adap->pin_scl, GPIO_DIRECTION_IN); |
| 29 | rc = gpio_get_pin_level(adap->pin_scl); |
| 30 | gpio_set_pin_direction(adap->pin_scl, GPIO_DIRECTION_OUT); |
| 31 | return rc; |
| 32 | } |
| 33 | |
| 34 | static inline void sdalo(const struct i2c_adapter *adap) |
| 35 | { |
| 36 | setsda(adap, 0); |
| 37 | delay_us((adap->udelay+1) / 2); |
| 38 | } |
| 39 | |
| 40 | static inline void sdahi(const struct i2c_adapter *adap) |
| 41 | { |
| 42 | setsda(adap, 1); |
| 43 | delay_us((adap->udelay+1) / 2); |
| 44 | } |
| 45 | |
| 46 | static inline void scllo(const struct i2c_adapter *adap) |
| 47 | { |
| 48 | setscl(adap, 0); |
| 49 | delay_us(adap->udelay / 2); |
| 50 | } |
| 51 | |
| 52 | |
| 53 | static int sclhi(const struct i2c_adapter *adap) |
| 54 | { |
| 55 | setscl(adap, 1); |
| 56 | |
| 57 | /* wait for slow slaves' clock stretching to complete */ |
| 58 | while (!getscl(adap)) { |
| 59 | /* FIXME: abort at some point */ |
| 60 | } |
| 61 | return 0; |
| 62 | } |
| 63 | |
| 64 | static void i2c_start(const struct i2c_adapter *adap) |
| 65 | { |
| 66 | /* Assert: SCL + SDA are high */ |
| 67 | setsda(adap, 0); /* set SDA to low */ |
| 68 | delay_us(adap->udelay); /* delay */ |
| 69 | scllo(adap); /* Set SCL to low */ |
| 70 | } |
| 71 | |
| 72 | static void i2c_repstart(const struct i2c_adapter *adap) |
| 73 | { |
| 74 | /* Assert: SCL is low */ |
| 75 | sdahi(adap); |
| 76 | sclhi(adap); |
| 77 | setsda(adap, 0); |
| 78 | delay_us(adap->udelay); |
| 79 | scllo(adap); |
| 80 | } |
| 81 | |
| 82 | static void i2c_stop(const struct i2c_adapter *adap) |
| 83 | { |
| 84 | /* Assert: SCL is low */ |
| 85 | sdalo(adap); /* set SDA low */ |
| 86 | sclhi(adap); /* set SCL to high */ |
| 87 | setsda(adap, 1); /* set SDA to high */ |
| 88 | delay_us(adap->udelay); /* delay */ |
| 89 | } |
| 90 | |
| 91 | static int i2c_outb(const struct i2c_adapter *adap, uint8_t outdata) |
| 92 | { |
| 93 | uint8_t sb; |
| 94 | int ack, i; |
| 95 | |
| 96 | /* Assert: SCL is low */ |
| 97 | for (i = 7; i >= 0; i--) { |
| 98 | sb = (outdata >> i) & 1; |
| 99 | setsda(adap, sb); |
| 100 | delay_us((adap->udelay + 1) / 2); |
| 101 | if (sclhi(adap) < 0) |
| 102 | return -ERR_TIMEOUT; |
| 103 | scllo(adap); |
| 104 | } |
| 105 | sdahi(adap); |
| 106 | if (sclhi(adap) < 0) |
| 107 | return -ERR_TIMEOUT; |
| 108 | ack = !getsda(adap); |
| 109 | scllo(adap); |
| 110 | return ack; |
| 111 | } |
| 112 | |
| 113 | static int i2c_inb(const struct i2c_adapter *adap) |
| 114 | { |
| 115 | uint8_t indata = 0; |
| 116 | int i; |
| 117 | |
| 118 | /* Assert: CSL is low */ |
| 119 | sdahi(adap); |
| 120 | for (i = 0; i < 8; i++) { |
| 121 | /* SCL high */ |
| 122 | if (sclhi(adap) < 0) |
| 123 | return -ERR_TIMEOUT; |
| 124 | indata = indata << 1; |
| 125 | if (getsda(adap)) |
| 126 | indata |= 0x01; |
| 127 | setscl(adap, 0); |
| 128 | if (i == 7) |
| 129 | delay_us(adap->udelay / 2); |
| 130 | else |
| 131 | delay_us(adap->udelay); |
| 132 | } |
| 133 | /* Assert: SCL is low */ |
| 134 | return indata; |
| 135 | } |
| 136 | |
| 137 | /*! Single-byte register write. Assumes 8bit register address + 8bit values */ |
| 138 | int i2c_write_reg(const struct i2c_adapter *adap, uint8_t addr, uint8_t reg, uint8_t val) |
| 139 | { |
| 140 | int rc; |
| 141 | |
| 142 | i2c_start(adap); |
| 143 | rc = i2c_outb(adap, addr << 1); |
| 144 | if (rc < 0) |
| 145 | goto out_stop; |
| 146 | rc = i2c_outb(adap, reg); |
| 147 | if (rc < 0) |
| 148 | goto out_stop; |
| 149 | rc = i2c_outb(adap, val); |
| 150 | out_stop: |
| 151 | i2c_stop(adap); |
| 152 | return rc; |
| 153 | } |
| 154 | |
| 155 | /*! Single-byte register read. Assumes 8bit register address + 8bit values */ |
| 156 | int i2c_read_reg(const struct i2c_adapter *adap, uint8_t addr, uint8_t reg) |
| 157 | { |
| 158 | int rc; |
| 159 | |
| 160 | i2c_start(adap); |
| 161 | rc = i2c_outb(adap, addr << 1); |
| 162 | if (rc < 0) |
| 163 | goto out_stop; |
| 164 | rc = i2c_outb(adap, reg); |
| 165 | if (rc < 0) |
| 166 | goto out_stop; |
| 167 | i2c_repstart(adap); |
| 168 | rc = i2c_outb(adap, addr << 1 | 1); |
| 169 | if (rc < 0) |
| 170 | goto out_stop; |
| 171 | rc = i2c_inb(adap); |
| 172 | out_stop: |
| 173 | i2c_stop(adap); |
| 174 | return rc; |
| 175 | } |
| 176 | |
| 177 | /*! Initialize a given I2C adapter/bus */ |
| 178 | int i2c_init(const struct i2c_adapter *adap) |
| 179 | { |
| 180 | gpio_set_pin_direction(adap->pin_sda, GPIO_DIRECTION_OUT); |
| 181 | gpio_set_pin_direction(adap->pin_scl, GPIO_DIRECTION_OUT); |
| 182 | |
| 183 | /* Bring bus to a known state. Looks like STOP if bus is not free yet */ |
| 184 | setscl(adap, 1); |
| 185 | delay_us(adap->udelay); |
| 186 | setsda(adap, 1); |
| 187 | |
| 188 | return 0; |
| 189 | } |