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Add an example that uses burst APIs (#512)
uses i2c_write_burst_blocking and i2c_read_burst_blocking
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/* | ||
* Copyright (c) 2021 Valentin Milea <[email protected]> | ||
* Copyright (c) 2023 Raspberry Pi (Trading) Ltd. | ||
* | ||
* SPDX-License-Identifier: BSD-3-Clause | ||
*/ | ||
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#include <hardware/i2c.h> | ||
#include <pico/i2c_slave.h> | ||
#include <pico/stdlib.h> | ||
#include <stdio.h> | ||
#include <string.h> | ||
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static const uint I2C_SLAVE_ADDRESS = 0x17; | ||
static const uint I2C_BAUDRATE = 100000; // 100 kHz | ||
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#ifdef i2c_default | ||
// For this example, we run both the master and slave from the same board. | ||
// You'll need to wire pin GP4 to GP6 (SDA), and pin GP5 to GP7 (SCL). | ||
static const uint I2C_SLAVE_SDA_PIN = PICO_DEFAULT_I2C_SDA_PIN; // 4 | ||
static const uint I2C_SLAVE_SCL_PIN = PICO_DEFAULT_I2C_SCL_PIN; // 5 | ||
static const uint I2C_MASTER_SDA_PIN = 6; | ||
static const uint I2C_MASTER_SCL_PIN = 7; | ||
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// The slave implements a 256 byte memory. To write a series of bytes, the master first | ||
// writes the memory address, followed by the data. The address is automatically incremented | ||
// for each byte transferred, looping back to 0 upon reaching the end. Reading is done | ||
// sequentially from the current memory address. | ||
static struct | ||
{ | ||
uint8_t mem[256]; | ||
uint8_t mem_address; | ||
bool mem_address_written; | ||
} context; | ||
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// Our handler is called from the I2C ISR, so it must complete quickly. Blocking calls / | ||
// printing to stdio may interfere with interrupt handling. | ||
static void i2c_slave_handler(i2c_inst_t *i2c, i2c_slave_event_t event) { | ||
switch (event) { | ||
case I2C_SLAVE_RECEIVE: // master has written some data | ||
if (!context.mem_address_written) { | ||
// writes always start with the memory address | ||
uint8_t by = i2c_read_byte_raw(i2c); | ||
context.mem_address = by; | ||
context.mem_address_written = true; | ||
} else { | ||
// save into memory | ||
uint8_t by = i2c_read_byte_raw(i2c); | ||
context.mem[context.mem_address] = by; | ||
context.mem_address++; | ||
} | ||
break; | ||
case I2C_SLAVE_REQUEST: // master is requesting data | ||
// load from memory | ||
i2c_write_byte_raw(i2c, context.mem[context.mem_address]); | ||
context.mem_address++; | ||
break; | ||
case I2C_SLAVE_FINISH: // master has signalled Stop / Restart | ||
context.mem_address_written = false; | ||
break; | ||
default: | ||
break; | ||
} | ||
} | ||
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static void setup_slave() { | ||
gpio_init(I2C_SLAVE_SDA_PIN); | ||
gpio_set_function(I2C_SLAVE_SDA_PIN, GPIO_FUNC_I2C); | ||
gpio_pull_up(I2C_SLAVE_SDA_PIN); | ||
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gpio_init(I2C_SLAVE_SCL_PIN); | ||
gpio_set_function(I2C_SLAVE_SCL_PIN, GPIO_FUNC_I2C); | ||
gpio_pull_up(I2C_SLAVE_SCL_PIN); | ||
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i2c_init(i2c0, I2C_BAUDRATE); | ||
// configure I2C0 for slave mode | ||
i2c_slave_init(i2c0, I2C_SLAVE_ADDRESS, &i2c_slave_handler); | ||
} | ||
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static void run_master() { | ||
gpio_init(I2C_MASTER_SDA_PIN); | ||
gpio_set_function(I2C_MASTER_SDA_PIN, GPIO_FUNC_I2C); | ||
// pull-ups are already active on slave side, this is just a fail-safe in case the wiring is faulty | ||
gpio_pull_up(I2C_MASTER_SDA_PIN); | ||
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gpio_init(I2C_MASTER_SCL_PIN); | ||
gpio_set_function(I2C_MASTER_SCL_PIN, GPIO_FUNC_I2C); | ||
gpio_pull_up(I2C_MASTER_SCL_PIN); | ||
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i2c_init(i2c1, I2C_BAUDRATE); | ||
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for (uint8_t mem_address = 0;; mem_address = (mem_address + 32) % 256) { | ||
char msg[32]; | ||
snprintf(msg, sizeof(msg), "Hello, I2C slave! - 0x%02X", mem_address); | ||
uint8_t msg_len = strlen(msg); | ||
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uint8_t buf[32]; | ||
buf[0] = mem_address; | ||
memcpy(buf + 1, msg, msg_len); | ||
// write message at mem_address | ||
printf("Write at 0x%02X: '%s'\n", mem_address, msg); | ||
for(int i = 0; i < (1 + msg_len); i++) { | ||
int count; | ||
if (i < (1 + msg_len - 1)) { | ||
count = i2c_write_burst_blocking(i2c1, I2C_SLAVE_ADDRESS, &buf[i], 1); | ||
sleep_ms(1); // gratuitous sleep for demonstration purposes - don't do this in real code! | ||
} else if (i == (1 + msg_len - 1)) { | ||
count = i2c_write_blocking(i2c1, I2C_SLAVE_ADDRESS, &buf[i], 1, false); | ||
} | ||
if (count != 1) { | ||
puts("Couldn't write to slave, please check your wiring!"); | ||
return; | ||
} | ||
} | ||
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// seek to mem_address | ||
int count = i2c_write_blocking(i2c1, I2C_SLAVE_ADDRESS, buf, 1, true); | ||
hard_assert(count == 1); | ||
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// partial read | ||
for(int i = 0; i < msg_len; i++) { | ||
if (count < (msg_len - 1)) { | ||
count = i2c_read_burst_blocking(i2c1, I2C_SLAVE_ADDRESS, buf + i, 1); | ||
sleep_ms(1); // gratuitous sleep for demonstration purposes - don't do this in real code! | ||
} else { | ||
count = i2c_read_blocking(i2c1, I2C_SLAVE_ADDRESS, buf + i, 1, false); | ||
} | ||
hard_assert(count == 1); | ||
} | ||
buf[msg_len] = '\0'; | ||
printf("Read at 0x%02X: '%s'\n", mem_address, buf); | ||
hard_assert(memcmp(buf, msg, msg_len) == 0); | ||
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puts(""); | ||
sleep_ms(2000); | ||
} | ||
} | ||
#endif | ||
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int main() { | ||
stdio_init_all(); | ||
#if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN) | ||
#warning i2c / slave_mem_i2c example requires a board with I2C pins | ||
puts("Default I2C pins were not defined"); | ||
return 0; | ||
#else | ||
puts("\nI2C slave example"); | ||
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setup_slave(); | ||
run_master(); | ||
#endif | ||
} |