SPI Slave: Example not work with other devices

[mauriciofarina]

Greetings,

I'm having some trouble implementing a SPI communication between the ESP32 (SLAVE) and the nrf51-dk (MASTER).

Basically, what I'm trying to do is sending a char array from the nrf51 to the ESP32. In order to do so, I'm running a Mbed SPI Master example and trying to receive the array with the esp-idf example (peripherals/spi_slave/receiver). Unfortunately, after the transmission is done, no valid information is received. I also notice that, in most of the cases, my RX buffer is empty or with just a random value on the first element of the array. I've tried connecting the MISO pin on the MOSI pin on each board, and, in both cases, the boards got able to send and receive their own transmissions.


The NRF51 mbed Code:

Code: [Select all] [Expand/Collapse]

1. #include <mbed.h>
2.  
3.  
4. Serial pc(USBTX, USBRX);  //UART
5. SPI spi(SPI_PSELMOSI0,SPI_PSELMISO0,SPI_PSELSCK0);//SPI
6. DigitalIn handshake(p23); //SPI Handshake Pin
7. DigitalOut cs(SPI_PSELSS0); //SPI Chip Select
8.  
9.  
10. int main() {
11.  
12.  
13.     cs = 1; //Disable Slave
14.  
15.     pc.baud(9600);  //UART Init
16.     pc.printf("Starting...\n\r");
17.  
18.     spi.format(8,3);  //SPI 8 bits, Mode 3
19.     spi.frequency(1000000); // 1 MHz clock
20.  
21.    
22.  
23.     while(1) {
24.        
25.       //RX TX Buffers
26.       char tx_buffer[128] = {"MASTER TX BUFFER"};
27.       char tx_length = 128;
28.       char rx_buffer[128] = {"MASTER RX BUFFER"};
29.       char rx_length = 128;
30.      
31.      
32.       cs = 0; //Enable Slave
33.  
34.       while(!handshake){} // Wait for slave to be available
35.  
36.       spi.write(tx_buffer, tx_length, rx_buffer, rx_length);  //Transmission
37.  
38.       cs = 1; // Disable Slave
39.  
40.  
41.       pc.printf("String:\n\r"); //Print RX Buffer
42.       for(i = 0; i < 128 ; i++){
43.         pc.printf("%c", rx_buffer[i]);
44.       }
45.       pc.printf("\n\r");
46.      
47.      
48.       wait(5); // Wait
49.  
50.     }
51. }

GeSHi © Codebox Plus Extension

On the ESP32 I'm running the SPI_Slave (Receiver) example with a few changes:

- SPI mode 3
- Added the Attribute WORD_ALIGNED_ATTR to recvbuf and sendbuf
- Changed the transmission String

Code: [Select all] [Expand/Collapse]

1. #include <stdio.h>
2. #include <stdint.h>
3. #include <stddef.h>
4. #include <string.h>
5.  
6. #include "freertos/FreeRTOS.h"
7. #include "freertos/task.h"
8. #include "freertos/semphr.h"
9. #include "freertos/queue.h"
10.  
11. #include "lwip/sockets.h"
12. #include "lwip/dns.h"
13. #include "lwip/netdb.h"
14. #include "lwip/igmp.h"
15.  
16. #include "esp_wifi.h"
17. #include "esp_system.h"
18. #include "esp_event.h"
19. #include "esp_event_loop.h"
20. #include "nvs_flash.h"
21. #include "soc/rtc_cntl_reg.h"
22. #include "esp32/rom/cache.h"
23. #include "driver/spi_slave.h"
24. #include "esp_log.h"
25. #include "esp_spi_flash.h"
26.  
27.  
28.  
29. #define GPIO_HANDSHAKE 2
30. #define GPIO_MOSI 12
31. #define GPIO_MISO 13
32. #define GPIO_SCLK 15
33. #define GPIO_CS 14
34.  
35.  
36. void my_post_setup_cb(spi_slave_transaction_t *trans) {
37.     WRITE_PERI_REG(GPIO_OUT_W1TS_REG, (1<<GPIO_HANDSHAKE));
38. }
39.  
40. void my_post_trans_cb(spi_slave_transaction_t *trans) {
41.     WRITE_PERI_REG(GPIO_OUT_W1TC_REG, (1<<GPIO_HANDSHAKE));
42. }
43.  
44. void app_main()
45. {
46.     int n=0;
47.     esp_err_t ret;
48.  
49.     spi_bus_config_t buscfg={
50.         .mosi_io_num=GPIO_MOSI,
51.         .miso_io_num=GPIO_MISO,
52.         .sclk_io_num=GPIO_SCLK
53.     };
54.  
55.     spi_slave_interface_config_t slvcfg={
56.         .mode=3,    // Changed to mode 3
57.         .spics_io_num=GPIO_CS,
58.         .queue_size=3,
59.         .flags=0,
60.         .post_setup_cb=my_post_setup_cb,
61.         .post_trans_cb=my_post_trans_cb
62.     };
63.  
64.     gpio_config_t io_conf={
65.         .intr_type=GPIO_INTR_DISABLE,
66.         .mode=GPIO_MODE_OUTPUT,
67.         .pin_bit_mask=(1<<GPIO_HANDSHAKE)
68.     };
69.  
70.     gpio_config(&io_conf);
71.  
72.     gpio_set_pull_mode(GPIO_MOSI, GPIO_PULLUP_ONLY);
73.     gpio_set_pull_mode(GPIO_SCLK, GPIO_PULLUP_ONLY);
74.     gpio_set_pull_mode(GPIO_CS, GPIO_PULLUP_ONLY);
75.  
76.     ret=spi_slave_initialize(HSPI_HOST, &buscfg, &slvcfg, 1);
77.     assert(ret==ESP_OK);
78.  
79.     WORD_ALIGNED_ATTR char sendbuf[129]=""; // Added the WORD ALIGNED Attribute
80.     WORD_ALIGNED_ATTR char recvbuf[129]="";
81.     memset(recvbuf, 0, 33);
82.     spi_slave_transaction_t t;
83.     memset(&t, 0, sizeof(t));
84.  
85.     while(1) {
86.         memset(recvbuf, 0xA5, 129);
87.         sprintf(sendbuf, "SLAVE TX BUFFER"); // Changed String
88.  
89.         t.length=128*8;
90.         t.tx_buffer=sendbuf;
91.         t.rx_buffer=recvbuf;
92.        
93.         ret=spi_slave_transmit(HSPI_HOST, &t, portMAX_DELAY);
94.  
95.         printf("Received: %s\n", recvbuf);
96.         n++;
97.     }
98.  
99. }

GeSHi © Codebox Plus Extension

Any ideas of what I'm doing wrong?

[JL1946]

By now, you have figured out that the error is in the Tx_length which is supposed to indicate the number of BITS being transmitted. You indicate a char of 128 bytes and a length of 128 - this should be 128*8 (Bytes*Bits). That is why your Receive Buffer is almost Empty - the sender is transmitting just 16 Bytes (16*8 = 128).