Added flexible payload to SPI example

examples/spi/host/src/host.c

@@ -1,18 +1,30 @@
 // Copyright 2016-2024 XMOS LIMITED.
 // This Software is subject to the terms of the XMOS Public Licence: Version 1.
+
+/*
+ * This example demonstrates sending a command to a device and reading it back.
+ * The control command utilizes a payload of size PAYLOAD_LEN bytes.
+ * The example verifies that the read-back value matches the written value(s).
+ */
+
 #include <stdio.h>
 #include <stdlib.h>
+#include <assert.h>
+
 #include "control_host.h"
+#include "control_transport_shared.h" // for SPI_DATA_MAX_BYTES
 #include "resource.h"
 #include "util.h"
 #include <bcm2835.h>
 
 #define INVALID_CONTROL_VERSION 0xFF
+#define PAYLOAD_LEN 1 // payload length in bytes
 
 int main(void)
 {
   control_version_t version = INVALID_CONTROL_VERSION;
-  unsigned char payload[4];
+  assert(PAYLOAD_LEN > 0 && PAYLOAD_LEN < SPI_DATA_MAX_BYTES);
+  unsigned char payload[PAYLOAD_LEN];
   uint8_t i;
 
   if (control_init_spi_pi(SPI_MODE_3, BCM2835_SPI_CLOCK_DIVIDER_8192, 2) != CONTROL_SUCCESS) {
@@ -31,27 +43,34 @@ int main(void)
   }
 
   printf("started\n");
+  printf("using payload of size %d\n", PAYLOAD_LEN);
 
   for (i = 0; i < 4; i++) {
-    payload[0] = i;
-    if (control_write_command(RESOURCE_ID, CONTROL_CMD_SET_WRITE(0), payload, 1) != CONTROL_SUCCESS) {
+    for (int j = 0; j < PAYLOAD_LEN; j++) {
+      payload[j] = i+j;
+
+    }
+
+    if (control_write_command(RESOURCE_ID, CONTROL_CMD_SET_WRITE(0), payload, PAYLOAD_LEN) != CONTROL_SUCCESS) {
       printf("control write command failed\n");
       exit(1);
     }
 
-    pause_short();
-
-    if (control_read_command(RESOURCE_ID, CONTROL_CMD_SET_READ(0), payload, 1) != CONTROL_SUCCESS) {
+    if (control_read_command(RESOURCE_ID, CONTROL_CMD_SET_READ(0), payload, PAYLOAD_LEN) != CONTROL_SUCCESS) {
       printf("control read command failed\n");
       exit(1);
     }
-
-    if (payload[0] != i) {
-      printf("control read command returned the wrong value, expected %d, returned %d\n", i, payload[0]);
-      exit(1);
+    for (int j = 0; j < PAYLOAD_LEN; j++) {
+      if (payload[j] != i+j) {
+        printf("control read command returned the wrong value, expected %d, returned %d\n", i+j, payload[j]);
+        exit(1);
+      }
     }
-    printf("Written and read back command with payload: 0x%02X\n", payload[0]);
-
+    printf("Written and read back command with payload: ");
+    for (int j = 0; j < PAYLOAD_LEN; j++) {
+      printf("%02X ", payload[j]);
+    }
+    printf("\n");
   }
 
   control_cleanup_spi();

examples/spi/src/app.xc

@@ -4,6 +4,7 @@
 #include <stdint.h>
 #include <assert.h>
 #include "control.h"
+#include "control_transport_shared.h" // Needed for SPI_DATA_MAX_BYTES
 #include "app.h"
 
 void app(server interface control i_control)
@@ -17,7 +18,7 @@ void app(server interface control i_control)
 #endif
 
   num_commands = 0;
-  uint8_t test_value = 0;
+  uint8_t test_values[SPI_DATA_MAX_BYTES] = {0};
   while (1) {
     select {
       case i_control.register_resources(control_resid_t resources[MAX_RESOURCES_PER_INTERFACE],
@@ -43,7 +44,9 @@ void app(server interface control i_control)
           ret = CONTROL_ERROR;
           break;
         }
-        test_value = payload[0];
+        for (int j = 0; j < payload_len; j++) {
+          test_values[j] = payload[j];
+        }
         ret = CONTROL_SUCCESS;
         break;
 
@@ -60,12 +63,11 @@ void app(server interface control i_control)
           ret = CONTROL_ERROR;
           break;
         }
-        if (payload_len != 1) {
-          printf("expecting 1 read byte, not %d\n", payload_len);
-          ret = CONTROL_ERROR;
-          break;
+
+        for (int j = 0; j < payload_len; j++) {
+          payload[j] = test_values[j];
         }
-        payload[0] = test_value;
+
         ret = CONTROL_SUCCESS;
         break;
     }