receiver sample
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Outline
#include <stdio.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"
#include "driver/spi_slave.h"
#include "driver/gpio.h"
#define RCV_HOST
#define RCV_HOST
#define GPIO_HANDSHAKE
#define GPIO_MOSI
#define GPIO_MISO
#define GPIO_SCLK
#define GPIO_CS
my_post_setup_cb(spi_slave_transaction_t *)
my_post_trans_cb(spi_slave_transaction_t *)
app_main()
Files
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SourceVuESP-IDF Framework and Examplesreceiver samplemain/app_main.c
 
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/* SPI Slave example, receiver (uses SPI Slave driver to communicate with sender) This example code is in the Public Domain (or CC0 licensed, at your option.) Unless required by applicable law or agreed to in writing, this software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. *//* ... */ #include <stdio.h> #include <stdint.h> #include <stddef.h> #include <string.h> #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "esp_log.h" #include "driver/spi_slave.h" #include "driver/gpio.h"9 includes /* SPI receiver (slave) example. This example is supposed to work together with the SPI sender. It uses the standard SPI pins (MISO, MOSI, SCLK, CS) to transmit data over in a full-duplex fashion, that is, while the master puts data on the MOSI pin, the slave puts its own data on the MISO pin. This example uses one extra pin: GPIO_HANDSHAKE is used as a handshake pin. After a transmission has been set up and we're ready to send/receive data, this code uses a callback to set the handshake pin high. The sender will detect this and start sending a transaction. As soon as the transaction is done, the line gets set low again. *//* ... */ ////////////////////////////////////////////////////////////////////////////////////////////////////////// ////////////// Please update the following configuration according to your HardWare spec ///////////////// ////////////////////////////////////////////////////////////////////////////////////////////////////////// #ifdef CONFIG_IDF_TARGET_ESP32 #define RCV_HOST HSPI_HOST #else #define RCV_HOST SPI2_HOST #endif #define GPIO_HANDSHAKE 2 #define GPIO_MOSI 12 #define GPIO_MISO 13 #define GPIO_SCLK 15 #define GPIO_CS 145 defines //Called after a transaction is queued and ready for pickup by master. We use this to set the handshake line high. void my_post_setup_cb(spi_slave_transaction_t *trans) { gpio_set_level(GPIO_HANDSHAKE, 1); }{ ... } //Called after transaction is sent/received. We use this to set the handshake line low. void my_post_trans_cb(spi_slave_transaction_t *trans) { gpio_set_level(GPIO_HANDSHAKE, 0); }{ ... } //Main application void app_main(void) { int n = 0; esp_err_t ret; //Configuration for the SPI bus spi_bus_config_t buscfg = { .mosi_io_num = GPIO_MOSI, .miso_io_num = GPIO_MISO, .sclk_io_num = GPIO_SCLK, .quadwp_io_num = -1, .quadhd_io_num = -1, }{...}; //Configuration for the SPI slave interface spi_slave_interface_config_t slvcfg = { .mode = 0, .spics_io_num = GPIO_CS, .queue_size = 3, .flags = 0, .post_setup_cb = my_post_setup_cb, .post_trans_cb = my_post_trans_cb }{...}; //Configuration for the handshake line gpio_config_t io_conf = { .intr_type = GPIO_INTR_DISABLE, .mode = GPIO_MODE_OUTPUT, .pin_bit_mask = BIT64(GPIO_HANDSHAKE), }{...}; //Configure handshake line as output gpio_config(&io_conf); //Enable pull-ups on SPI lines so we don't detect rogue pulses when no master is connected. gpio_set_pull_mode(GPIO_MOSI, GPIO_PULLUP_ONLY); gpio_set_pull_mode(GPIO_SCLK, GPIO_PULLUP_ONLY); gpio_set_pull_mode(GPIO_CS, GPIO_PULLUP_ONLY); //Initialize SPI slave interface ret = spi_slave_initialize(RCV_HOST, &buscfg, &slvcfg, SPI_DMA_CH_AUTO); assert(ret == ESP_OK); char *sendbuf = spi_bus_dma_memory_alloc(RCV_HOST, 129, 0); char *recvbuf = spi_bus_dma_memory_alloc(RCV_HOST, 129, 0); assert(sendbuf && recvbuf); spi_slave_transaction_t t = {0}; while (1) { //Clear receive buffer, set send buffer to something sane memset(recvbuf, 0xA5, 129); sprintf(sendbuf, "This is the receiver, sending data for transmission number %04d.", n); //Set up a transaction of 128 bytes to send/receive t.length = 128 * 8; t.tx_buffer = sendbuf; t.rx_buffer = recvbuf; /* This call enables the SPI slave interface to send/receive to the sendbuf and recvbuf. The transaction is initialized by the SPI master, however, so it will not actually happen until the master starts a hardware transaction by pulling CS low and pulsing the clock etc. In this specific example, we use the handshake line, pulled up by the .post_setup_cb callback that is called as soon as a transaction is ready, to let the master know it is free to transfer data. *//* ... */ ret = spi_slave_transmit(RCV_HOST, &t, portMAX_DELAY); //spi_slave_transmit does not return until the master has done a transmission, so by here we have sent our data and //received data from the master. Print it. printf("Received: %s\n", recvbuf); n++; }{...} }{ ... }
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