/* * Copyright (c) 2021 Valentin Milea <valentin.milea@gmail.com> * Copyright (c) 2023 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <hardware/i2c.h> #include <pico/i2c_slave.h> #include <pico/stdlib.h> #include <stdio.h> #include <string.h> static const uint I2C_SLAVE_ADDRESS = 0x17; static const uint I2C_BAUDRATE = 100000; // 100 kHz #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; // 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; // 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; } } 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); gpio_init(I2C_SLAVE_SCL_PIN); gpio_set_function(I2C_SLAVE_SCL_PIN, GPIO_FUNC_I2C); gpio_pull_up(I2C_SLAVE_SCL_PIN); i2c_init(i2c0, I2C_BAUDRATE); // configure I2C0 for slave mode i2c_slave_init(i2c0, I2C_SLAVE_ADDRESS, &i2c_slave_handler); } 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); gpio_init(I2C_MASTER_SCL_PIN); gpio_set_function(I2C_MASTER_SCL_PIN, GPIO_FUNC_I2C); gpio_pull_up(I2C_MASTER_SCL_PIN); i2c_init(i2c1, I2C_BAUDRATE); 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); 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; } } // seek to mem_address int count = i2c_write_blocking(i2c1, I2C_SLAVE_ADDRESS, buf, 1, true); hard_assert(count == 1); // 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); puts(""); sleep_ms(2000); } } #endif 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"); setup_slave(); run_master(); #endif }

This firmware image was imported from the pico-examples repository. 


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