drivers/at: parse +CME/+CMS responses and save error value

drivers/at/at.c

@@ -41,6 +41,7 @@
 
 #include <assert.h>
 #include <errno.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "at.h"
@@ -77,6 +78,18 @@ static void _event_process_urc(event_t *_event)
 }
 #endif
 
+static ssize_t at_readline_skip_empty_stop_at_str(at_dev_t *dev, char *resp_buf,
+                                                  size_t len, bool keep_eol,
+                                                  char const *substr, uint32_t timeout);
+static size_t at_readline_stop_at_str(at_dev_t *dev, char *resp_buf, size_t len,
+                                      bool keep_eol, char const *substr,
+                                      uint32_t timeout);
+
+static inline bool starts_with(char const *str, char const *prefix)
+{
+    return strncmp(str, prefix, strlen(prefix)) == 0;
+}
+
 static void _isrpipe_write_one_wrapper(void *_dev, uint8_t data)
 {
     at_dev_t *dev = (at_dev_t *) _dev;
@@ -88,18 +101,50 @@ static void _isrpipe_write_one_wrapper(void *_dev, uint8_t data)
 #endif
 }
 
-int at_dev_init(at_dev_t *dev, uart_t uart, uint32_t baudrate, char *buf, size_t bufsize)
+int at_dev_init(at_dev_t *dev, at_dev_init_t const *init)
 {
-    dev->uart = uart;
+    dev->uart = init->uart;
+    assert(init->rp_buf_size >= 16);
+    dev->rp_buf = init->rp_buf;
+    dev->rp_buf_size = init->rp_buf_size;
 
 #if IS_USED(MODULE_AT_URC_ISR)
     dev->awaiting_response = false;
     dev->event.handler = _event_process_urc;
 #endif
 
-    isrpipe_init(&dev->isrpipe, (uint8_t *)buf, bufsize);
+    isrpipe_init(&dev->isrpipe, (uint8_t *)init->rx_buf, init->rx_buf_size);
 
-    return uart_init(uart, baudrate, _isrpipe_write_one_wrapper, dev);
+    return uart_init(init->uart, init->baudrate, _isrpipe_write_one_wrapper, dev);
+}
+
+int at_parse_resp(at_dev_t *dev, char const *resp)
+{
+    if (*resp == '\0') {
+        return 1;
+    }
+    if (starts_with(resp, CONFIG_AT_RECV_OK)) {
+        dev->rp_buf[0] = '\0';
+        return 0;
+    }
+    if (starts_with(resp, CONFIG_AT_RECV_ERROR)) {
+        return -1;
+    }
+    /* A specific command may return either CME or CMS, we need not differentiate */
+    if (!starts_with(resp, "+CME ERROR: ") &&
+        !starts_with(resp, "+CMS ERROR: ")) {
+        /* neither `OK` nor error, must be a response or URC */
+        return 1;
+    }
+
+    resp += strlen("+CMx ERROR: ");
+    size_t resp_len = strlen(resp);
+    if (resp_len + 1 > dev->rp_buf_size) {
+        return -ENOBUFS;
+    }
+    /* dev->rp_buf and resp may overlap */
+    memmove(dev->rp_buf, resp, resp_len + 1);
+    return -AT_ERR_EXTENDED;
 }
 
 int at_expect_bytes(at_dev_t *dev, const char *bytes, uint32_t timeout)
@@ -224,8 +269,7 @@ int at_send_cmd(at_dev_t *dev, const char *command, uint32_t timeout)
             return -1;
         }
 
-        if (at_expect_bytes(dev, CONFIG_AT_SEND_EOL AT_RECV_EOL_1 AT_RECV_EOL_2,
+        if (at_expect_bytes(dev, CONFIG_AT_SEND_EOL, timeout)) {
-                            timeout)) {
             return -2;
         }
     }
@@ -275,53 +319,64 @@ ssize_t at_send_cmd_get_resp_wait_ok(at_dev_t *dev, const char *command, const c
 {
     ssize_t res;
     ssize_t res_ok;
-    char ok_buf[64];
 
     at_drain(dev);
 
     res = at_send_cmd(dev, command, timeout);
     if (res) {
-        goto out;
+        return res;
     }
 
     /* URCs may occur right after the command has been sent and before the
      * expected response */
-    do {
+    while ((res = at_readline_skip_empty(dev, resp_buf, len, false, timeout)) >= 0) {
-        res = at_readline_skip_empty(dev, resp_buf, len, false, timeout);
+        if (!resp_prefix || *resp_prefix == '\0') {
-
+            break;
+        }
         /* Strip the expected prefix */
-        if (res > 0 && resp_prefix && *resp_prefix) {
+        size_t prefix_len = strlen(resp_prefix);
-            size_t prefix_len = strlen(resp_prefix);
+        if (starts_with(resp_buf, resp_prefix)) {
-            if (strncmp(resp_buf, resp_prefix, prefix_len) == 0) {
+            size_t remaining_len = strlen(resp_buf) - prefix_len;
-                size_t remaining_len = strlen(resp_buf) - prefix_len;
+            /* The one extra byte in the copy is the terminating nul byte */
-                /* The one extra byte in the copy is the terminating nul byte */
+            memmove(resp_buf, resp_buf + prefix_len, remaining_len + 1);
-                memmove(resp_buf, resp_buf + prefix_len, remaining_len + 1);
+            res -= prefix_len;
-                res -= prefix_len;
+            break;
-                break;
-            }
         }
-    } while (res >= 0);
+        res = at_parse_resp(dev, resp_buf);
-
+        if (res == 0) {
-    /* wait for OK */
+            /* empty response */
-    if (res >= 0) {
+            return 0;
-        res_ok = at_readline_skip_empty(dev, ok_buf, sizeof(ok_buf), false, timeout);
-        if (res_ok < 0) {
-            return -1;
         }
-        ssize_t len_ok = sizeof(CONFIG_AT_RECV_OK) - 1;
+        if (res < 0) {
-        if ((len_ok != 0) && (strcmp(ok_buf, CONFIG_AT_RECV_OK) == 0)) {
+            return res;
         }
+#if IS_USED(MODULE_AT_URC)
         else {
-            /* Something else than OK */
+            clist_foreach(&dev->urc_list, _check_urc, resp_buf);
-            res = -1;
         }
+#endif
     }
-out:
+    if (res < 0) {
-    return res;
+        return res;
+    }
+    /* wait for OK */
+    res_ok = at_readline_skip_empty(dev, dev->rp_buf, dev->rp_buf_size, false, timeout);
+    if (res_ok < 0) {
+        return -1;
+    }
+    res_ok = at_parse_resp(dev, dev->rp_buf);
+    if (res_ok == 0) {
+        return res;
+    }
+    if (res_ok < 0) {
+        return res_ok;
+    }
+    /* Neither OK nor error, go figure... */
+    return -1;
 }
 
-ssize_t at_send_cmd_get_lines(at_dev_t *dev, const char *command,
+ssize_t at_send_cmd_get_lines(at_dev_t *dev, const char *command, char *resp_buf,
-                              char *resp_buf, size_t len, bool keep_eol, uint32_t timeout)
+                              size_t len, bool keep_eol, uint32_t timeout)
 {
     const char eol[] = AT_RECV_EOL_1 AT_RECV_EOL_2;
     assert(sizeof(eol) > 1);
@@ -334,123 +389,113 @@ ssize_t at_send_cmd_get_lines(at_dev_t *dev, const char *command,
 
     res = at_send_cmd(dev, command, timeout);
     if (res) {
-        goto out;
+        return res;
     }
 
     memset(resp_buf, '\0', len);
 
-    while (1) {
+    bool first_line = true;
-        res = at_readline(dev, pos, bytes_left, keep_eol, timeout);
+    while (bytes_left) {
+        if (first_line) {
+            res = at_readline_skip_empty(dev, pos, bytes_left, keep_eol, timeout);
+            first_line = false;
+        } else {
+            /* keep subsequent empty lines, for whatever reason */
+            res = at_readline(dev, pos, bytes_left, keep_eol, timeout);
+        }
         if (res == 0) {
-            if (bytes_left) {
+            *pos++ = eol[sizeof(eol) - 2];
-                *pos++ = eol[sizeof(eol) - 2];
+            bytes_left--;
-                bytes_left--;
-            }
             continue;
         }
         else if (res > 0) {
-            bytes_left -= res;
+            size_t const res_len = res;
-            size_t len_ok = sizeof(CONFIG_AT_RECV_OK) - 1;
+            bytes_left -= res_len;
-            size_t len_error = sizeof(CONFIG_AT_RECV_ERROR) - 1;
+            res = at_parse_resp(dev, pos);
-            if (((size_t )res == (len_ok + keep_eol)) &&
+
-                (len_ok != 0) &&
+            switch (res) {
-                (strncmp(pos, CONFIG_AT_RECV_OK, len_ok) == 0)) {
+            case 0: /* OK */
                 res = len - bytes_left;
-                break;
+                return res;
-            }
+            case 1: /* response or URC */
-            else if (((size_t )res == (len_error + keep_eol)) &&
+                pos += res_len;
-                     (len_error != 0) &&
+                if (bytes_left == 0) {
-                     (strncmp(pos, CONFIG_AT_RECV_ERROR, len_error) == 0)) {
+                    return -ENOBUFS;
-                return -1;
-            }
-            else if (strncmp(pos, "+CME ERROR:", 11) == 0) {
-                return -2;
-            }
-            else if (strncmp(pos, "+CMS ERROR:", 11) == 0) {
-                return -2;
-            }
-            else {
-                pos += res;
-                if (bytes_left) {
-                    *pos++ = eol[sizeof(eol) - 2];
-                    bytes_left--;
-                }
-                else {
-                    return -1;
                 }
+                *pos++ = eol[sizeof(eol) - 2];
+                bytes_left--;
+                continue;
+            default: /* <0 */
+                return res;
             }
         }
         else {
-            break;
+            return res;
         }
     }
 
-out:
+    return -ENOBUFS;
-    return res;
 }
 
 int at_send_cmd_wait_prompt(at_dev_t *dev, const char *command, uint32_t timeout)
 {
-    unsigned cmdlen = strlen(command);
-
     at_drain(dev);
 
-    uart_write(dev->uart, (const uint8_t *)command, cmdlen);
+    int res = at_send_cmd(dev, command, timeout);
-    uart_write(dev->uart, (const uint8_t *)CONFIG_AT_SEND_EOL, AT_SEND_EOL_LEN);
+    if (res) {
-
+        return res;
-    if (!IS_ACTIVE(CONFIG_AT_SEND_SKIP_ECHO)) {
-        if (at_wait_bytes(dev, command, timeout)) {
-            return -1;
-        }
-        if (at_expect_bytes(dev, CONFIG_AT_SEND_EOL, timeout)) {
-            return -2;
-        }
     }
 
-    return at_wait_bytes(dev, ">", timeout);
+    do {
+        res = at_readline_skip_empty_stop_at_str(dev, dev->rp_buf, dev->rp_buf_size,
+                                                 false, ">", timeout);
+        if (res < 0) {
+            break;
+        }
+        if (strstr(dev->rp_buf, ">")) {
+            return 0;
+        }
+        res = at_parse_resp(dev, dev->rp_buf);
+#ifdef MODULE_AT_URC
+        if (res == 1) {
+            clist_foreach(&dev->urc_list, _check_urc, dev->rp_buf);
+        }
+#endif
+    } while (res >= 0);
+
+    return res;
 }
 
 int at_send_cmd_wait_ok(at_dev_t *dev, const char *command, uint32_t timeout)
 {
     int res;
-    char resp_buf[64];
 
-    res = at_send_cmd_get_resp(dev, command, resp_buf, sizeof(resp_buf),
+    res = at_send_cmd_get_resp(dev, command, dev->rp_buf, dev->rp_buf_size, timeout);
-                               timeout);
-
-    size_t const len_ok = sizeof(CONFIG_AT_RECV_OK) - 1;
-    size_t const len_err = sizeof(CONFIG_AT_RECV_ERROR) - 1;
-    size_t const len_cme_cms = sizeof("+CME ERROR:") - 1;
 
     while (res >= 0) {
-        if (strncmp(resp_buf, CONFIG_AT_RECV_OK, len_ok) == 0) {
+        res = at_parse_resp(dev, dev->rp_buf);
-            return 0;
+        if (res < 1) {
+            return res;
         }
-        else if (strncmp(resp_buf, CONFIG_AT_RECV_ERROR, len_err) == 0) {
-            return -1;
-        }
-        else if (strncmp(resp_buf, "+CME ERROR:", len_cme_cms) == 0) {
-            return -2;
-        }
-        else if (strncmp(resp_buf, "+CMS ERROR:", len_cme_cms) == 0) {
-            return -2;
-        }
-        /* probably a sneaky URC */
 #ifdef MODULE_AT_URC
-        clist_foreach(&dev->urc_list, _check_urc, resp_buf);
+        clist_foreach(&dev->urc_list, _check_urc, dev->rp_buf);
 #endif
-        res = at_readline_skip_empty(dev, resp_buf, sizeof(resp_buf), false, timeout);
+        res = at_readline_skip_empty(dev, dev->rp_buf, dev->rp_buf_size, false, timeout);
     }
 
     return res;
 }
 
-ssize_t at_readline(at_dev_t *dev, char *resp_buf, size_t len, bool keep_eol, uint32_t timeout)
+/* Used to detect a substring that may happen before the EOL. For example,
+ * Ublox LTE modules don't add EOL after the prompt character `>`. */
+static size_t at_readline_stop_at_str(at_dev_t *dev, char *resp_buf, size_t len,
+                                      bool keep_eol, char const *substr,
+                                      uint32_t timeout)
 {
     const char eol[] = AT_RECV_EOL_1 AT_RECV_EOL_2;
     assert(sizeof(eol) > 1);
 
-    ssize_t res = -1;
+    ssize_t res = 0;
     char *resp_pos = resp_buf;
 
 #if IS_USED(MODULE_AT_URC_ISR)
@@ -458,8 +503,15 @@ ssize_t at_readline(at_dev_t *dev, char *resp_buf, size_t len, bool keep_eol, ui
 #endif
 
     memset(resp_buf, 0, len);
-
+    size_t substr_len = 0;
-    while (len) {
+    if (substr) {
+        substr_len = strlen(substr);
+        if (substr_len == 0) {
+            return -EINVAL;
+        }
+    }
+    char const *substr_p = resp_buf;
+    while (len > 1) {
         int read_res;
         if ((read_res = isrpipe_read_timeout(&dev->isrpipe, (uint8_t *)resp_pos,
                                              1, timeout)) == 1) {
@@ -473,12 +525,19 @@ ssize_t at_readline(at_dev_t *dev, char *resp_buf, size_t len, bool keep_eol, ui
             }
             if (*resp_pos == eol[sizeof(eol) - 2]) {
                 *resp_pos = '\0';
-                res = resp_pos - resp_buf;
+                break;
-                goto out;
             }
 
             resp_pos += read_res;
             len -= read_res;
+
+            if (substr && (size_t)(resp_pos - resp_buf) >= substr_len) {
+                if (strncmp(substr_p, substr, substr_len) == 0) {
+                    break;
+                } else {
+                    substr_p++;
+                }
+            }
         }
         else if (read_res == -ETIMEDOUT) {
             res = -ETIMEDOUT;
@@ -486,28 +545,59 @@ ssize_t at_readline(at_dev_t *dev, char *resp_buf, size_t len, bool keep_eol, ui
         }
     }
 
-out:
 #if IS_USED(MODULE_AT_URC_ISR)
     dev->awaiting_response = false;
 #endif
 
     if (res < 0) {
         *resp_buf = '\0';
+    } else {
+        res = resp_pos - resp_buf;
     }
     return res;
 }
 
+ssize_t at_readline(at_dev_t *dev, char *resp_buf, size_t len, bool keep_eol,
+                    uint32_t timeout)
+{
+    return at_readline_stop_at_str(dev, resp_buf, len, keep_eol, NULL, timeout);
+}
+
+static ssize_t at_readline_skip_empty_stop_at_str(at_dev_t *dev, char *resp_buf,
+                                                  size_t len, bool keep_eol,
+                                                  char const *substr, uint32_t timeout)
+{
+    ssize_t res = at_readline_stop_at_str(dev, resp_buf, len, keep_eol, substr, timeout);
+    if (res == 0) {
+        /* skip possible empty line */
+        res = at_readline_stop_at_str(dev, resp_buf, len, keep_eol, substr, timeout);
+    }
+    return res;
+
+}
 ssize_t at_readline_skip_empty(at_dev_t *dev, char *resp_buf, size_t len,
                                bool keep_eol, uint32_t timeout)
 {
-    ssize_t res = at_readline(dev, resp_buf, len, keep_eol, timeout);
+    return at_readline_skip_empty_stop_at_str(dev, resp_buf, len, keep_eol, NULL, timeout);
-    if (res == 0) {
-        /* skip possible empty line */
-        res = at_readline(dev, resp_buf, len, keep_eol, timeout);
-    }
-    return res;
 }
 
+int at_wait_ok(at_dev_t *dev, uint32_t timeout)
+{
+    while (1) {
+        ssize_t res = at_readline_skip_empty(dev, dev->rp_buf, dev->rp_buf_size,
+                                            false, timeout);
+        if (res < 0) {
+            return res;
+        }
+        res = at_parse_resp(dev, dev->rp_buf);
+        if (res < 1) {
+            return res;
+        }
+#ifdef MODULE_AT_URC
+        clist_foreach(&dev->urc_list, _check_urc, dev->rp_buf);
+#endif
+    }
+}
 #ifdef MODULE_AT_URC
 void at_add_urc(at_dev_t *dev, at_urc_t *urc)
 {
@@ -531,7 +621,7 @@ static int _check_urc(clist_node_t *node, void *arg)
 
     DEBUG("Trying to match with %s\n", urc->code);
 
-    if (strncmp(buf, urc->code, strlen(urc->code)) == 0) {
+    if (starts_with(buf, urc->code)) {
         urc->cb(urc->arg, buf);
         return 1;
     }

drivers/include/at.h

@@ -17,10 +17,10 @@
  * intended to send, and bail out if there's no match.
  *
  * Furthermore, the library tries to cope with difficulties regarding different
- * line endings. It usually sends "<command><CR>", but expects
+ * line endings. It usually sends `<command><CR>`, but expects
- * "<command>\LF\CR" as echo.
+ * `<command>\LF\CR` as echo.
  *
- * As a debugging aid, when compiled with "-DAT_PRINT_INCOMING=1", every input
+ * As a debugging aid, when compiled with `-DAT_PRINT_INCOMING=1`, every input
  * byte gets printed.
  *
  * ## Unsolicited Result Codes (URC) ##
@@ -44,6 +44,24 @@
  * character is detected and there is no pending response. This works by posting
  * an @ref sys_event "event" to an event thread that processes the URCs.
  *
+ * ## Error reporting ##
+ * Most DCEs (Data Circuit-terminating Equipment, aka modem) can return extra error
+ * information instead of the rather opaque "ERROR" message. They have the form:
+ *  - `+CMS ERROR: err_code>` for SMS-related commands
+ *  - `+CME ERROR: <err_code>` for other commands
+ *
+ * For `+CME`, this behavior is usually off by default and can be toggled with:
+ *  `AT+CMEE=<type>`
+ * where `<type>` may be:
+ *  - 0 disable extended error reporting, return `ERROR`
+ *  - 1 enable extended error reporting, with `<err_code>` integer
+ *  - 2 enable extended error reporting, with `<err_code>` as string
+ * Check your DCE's manual for more information.
+ *
+ * Some of the API calls below support detailed error reporting. Whenever they
+ * detect extended error responses, -AT_ERR_EXTENDED is returned and `<err_code>`
+ * can be retrieved by calling @ref at_get_err_info().
+ *
  * @{
  *
  * @file
@@ -168,6 +186,9 @@ typedef struct {
 
 #endif /* MODULE_AT_URC */
 
+/** Error cause can be further investigated. */
+#define AT_ERR_EXTENDED 200
+
 /** Shortcut for getting send end of line length */
 #define AT_SEND_EOL_LEN  (sizeof(CONFIG_AT_SEND_EOL) - 1)
 
@@ -177,6 +198,8 @@ typedef struct {
 typedef struct {
     isrpipe_t isrpipe;      /**< isrpipe used for getting data from uart */
     uart_t uart;            /**< UART device where the AT device is attached */
+    char *rp_buf;           /**< response parsing buffer */
+    size_t rp_buf_size;     /**< response parsing buffer size */
 #ifdef MODULE_AT_URC
     clist_node_t urc_list;  /**< list to keep track of all registered urc's */
 #ifdef MODULE_AT_URC_ISR
@@ -186,19 +209,49 @@ typedef struct {
 #endif
 } at_dev_t;
 
+/**
+ * @brief AT device initialization parameters
+*/
+typedef struct {
+    uart_t uart;            /**< UART device where the AT device is attached */
+    uint32_t baudrate;      /**< UART device baudrate */
+    char *rx_buf;           /**< UART rx buffer */
+    size_t rx_buf_size;     /**< UART rx buffer size */
+    /**
+     * Response parsing buffer - used for classifying DCE responses and holding
+     * detailed error information. Must be at least 16 bytes.
+     * If you don't care about URCs (MODULE_AT_URC is undefined) this must only
+     * be large enough to hold responses like `OK`, `ERROR` or `+CME ERROR: <err_code>`.
+     * Otherwise adapt its size to the maximum length of the URCs you are expecting
+     * and actually care about. */
+    char *rp_buf;
+    size_t rp_buf_size;     /**< response parsing buffer size */
+} at_dev_init_t;
+
+/**
+ * @brief Get extended error information of the last command sent.
+ *
+ * If a previous at_* method returned with -AT_ERR_EXTENDED, you can retrieve
+ * a pointer to the error string with this.
+ *
+ * @param[in] dev device to operate on
+ *
+ * @retval string containing the error value.
+ */
+static inline char const *at_get_err_info(at_dev_t *dev)
+{
+    return dev->rp_buf;
+}
 /**
  * @brief   Initialize AT device struct
  *
  * @param[in]   dev         struct to initialize
- * @param[in]   uart        UART the device is connected to
+ * @param[in]   init        init struct, may be destroyed after return
- * @param[in]   baudrate    baudrate of the device
- * @param[in]   buf         input buffer
- * @param[in]   bufsize     size of @p buf
  *
  * @retval     success code UART_OK on success
  * @retval     error code UART_NODEV or UART_NOBAUD otherwise
  */
-int at_dev_init(at_dev_t *dev, uart_t uart, uint32_t baudrate, char *buf, size_t bufsize);
+int at_dev_init(at_dev_t *dev, at_dev_init_t const *init);
 
 /**
  * @brief   Simple command helper
@@ -210,7 +263,9 @@ int at_dev_init(at_dev_t *dev, uart_t uart, uint32_t baudrate, char *buf, size_t
  * @param[in]   timeout timeout (in usec)
  *
  * @retval      0 when device answers "OK"
- * @retval     <0 otherwise
+ * @retval     -AT_ERR_EXTENDED if failed and a error code can be retrieved with
+ *              @ref at_get_err_info() (i.e. DCE answered with `CMx ERROR`)
+ * @retval     <0 other failures
  */
 int at_send_cmd_wait_ok(at_dev_t *dev, const char *command, uint32_t timeout);
 
@@ -220,12 +275,14 @@ int at_send_cmd_wait_ok(at_dev_t *dev, const char *command, uint32_t timeout);
  * This function sends the supplied @p command, then waits for the prompt (>)
  * character and returns
  *
- * @param[in]   dev     device to operate on
+ * @param[in]   dev         device to operate on
- * @param[in]   command command string to send
+ * @param[in]   command     command string to send
- * @param[in]   timeout timeout (in usec)
+ * @param[in]   timeout     timeout (in usec)
  *
- * @retval       0 when prompt is received
+ * @retval      0 when prompt is received
- * @retval      <0 otherwise
+ * @retval     -AT_ERR_EXTENDED if failed and a error code can be retrieved with
+ *              @ref at_get_err_info() (i.e. DCE answered with `CMx ERROR`)
+ * @retval     <0 other failures
  */
 int at_send_cmd_wait_prompt(at_dev_t *dev, const char *command, uint32_t timeout);
 
@@ -246,7 +303,8 @@ int at_send_cmd_wait_prompt(at_dev_t *dev, const char *command, uint32_t timeout
  * @retval      n length of response on success
  * @retval     <0 on error
  */
-ssize_t at_send_cmd_get_resp(at_dev_t *dev, const char *command, char *resp_buf, size_t len, uint32_t timeout);
+ssize_t at_send_cmd_get_resp(at_dev_t *dev, const char *command, char *resp_buf,
+                             size_t len, uint32_t timeout);
 
 /**
  * @brief   Send AT command, wait for response plus OK
@@ -264,7 +322,9 @@ ssize_t at_send_cmd_get_resp(at_dev_t *dev, const char *command, char *resp_buf,
  * @param[in]   timeout     timeout (in usec)
  *
  * @retval      n length of response on success
- * @retval     <0 on error
+ * @retval     -AT_ERR_EXTENDED if failed and a error code can be retrieved with
+ *              @ref at_get_err_info() (i.e. DCE answered with `CMx ERROR`)
+ * @retval     <0 other failures
  */
 ssize_t at_send_cmd_get_resp_wait_ok(at_dev_t *dev, const char *command, const char *resp_prefix,
                                      char *resp_buf, size_t len, uint32_t timeout);
@@ -275,9 +335,8 @@ ssize_t at_send_cmd_get_resp_wait_ok(at_dev_t *dev, const char *command, const c
  * This function sends the supplied @p command, then returns all response
  * lines until the device sends "OK".
  *
- * If a line starts with "ERROR" or the buffer is full, the function returns -1.
+ * If a line contains a DTE error response, this function stops and returns
- * If a line starts with "+CME ERROR" or +CMS ERROR", the function returns -2.
+ * accordingly.
- * In this case resp_buf contains the error string.
  *
  * @param[in]   dev         device to operate on
  * @param[in]   command     command to send
@@ -287,8 +346,9 @@ ssize_t at_send_cmd_get_resp_wait_ok(at_dev_t *dev, const char *command, const c
  * @param[in]   timeout     timeout (in usec)
  *
  * @retval      n length of response on success
- * @retval     -1 on error
+ * @retval     -AT_ERR_EXTENDED if failed and a error code can be retrieved with
- * @retval     -2 on CMS or CME error
+ *              @ref at_get_err_info() (i.e. DCE answered with `CMx ERROR`)
+ * @retval     <0 other failures
  */
 ssize_t at_send_cmd_get_lines(at_dev_t *dev, const char *command, char *resp_buf,
                               size_t len, bool keep_eol, uint32_t timeout);
@@ -369,6 +429,22 @@ ssize_t at_recv_bytes(at_dev_t *dev, char *bytes, size_t len, uint32_t timeout);
  */
 int at_send_cmd(at_dev_t *dev, const char *command, uint32_t timeout);
 
+/**
+ * @brief   Parse a response from the device.
+ *
+ * This is always called automatically in functions that may return -AT_ERR_EXTENDED.
+ * However, if you read the response by other methods (e.g. with @ref at_recv_bytes()),
+ * you might want to call this on the response so that you don't have to parse it yourself.
+ *
+ * @retval  0 if the response is "OK"
+ * @retval -AT_ERR_EXTENDED if the response is `+CMx ERROR: <err>`, and `<err>`
+ *          has been successfully copied to @p dev->rp_buf
+ * @retval -1 if the response is "ERROR", or `+CMx ERROR: <err>` but `<err>`
+ *          could not be copied
+ * @retval  1 otherwise
+ */
+int at_parse_resp(at_dev_t *dev, char const *resp);
+
 /**
  * @brief   Read a line from device
  *
@@ -398,6 +474,21 @@ ssize_t at_readline(at_dev_t *dev, char *resp_buf, size_t len, bool keep_eol, ui
 ssize_t at_readline_skip_empty(at_dev_t *dev, char *resp_buf, size_t len,
                                bool keep_eol, uint32_t timeout);
 
+/**
+ * @brief Wait for an OK response.
+ *
+ * Useful when crafting the command-response sequence by yourself.
+ *
+ * @param[in]   dev     device to operate on
+ * @param[in]   timeout timeout (in usec)
+ *
+ * @retval      0 when device answers "OK"
+ * @retval     -AT_ERR_EXTENDED if failed and a error code can be retrieved with
+ *              @ref at_get_err_info() (i.e. DCE answered with `CMx ERROR`)
+ * @retval     <0 other failures
+ */
+int at_wait_ok(at_dev_t *dev, uint32_t timeout);
+
 /**
  * @brief   Drain device input buffer
  *

tests/drivers/at/Makefile

@@ -2,7 +2,14 @@ include ../Makefile.drivers_common
 
 USEMODULE += shell
 USEMODULE += at
-USEMODULE += at_urc_isr_medium
+USEMODULE += at_urc
+
+# Enable if the DCE is sending only \n for EOL
+# CFLAGS += -DAT_RECV_EOL_1=""
+
+# Enable this to test with echo off. Don't forget to disable echo in
+# 'tests-with-config/emulated_dce.py' too!
+# CFLAGS += -DCONFIG_AT_SEND_SKIP_ECHO=1
 
 # we are printing from the event thread, we need more stack
 CFLAGS += -DEVENT_THREAD_MEDIUM_STACKSIZE=1024

tests/drivers/at/main.c

@@ -20,6 +20,7 @@
  * @}
  */
 
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -33,6 +34,7 @@
 static at_dev_t at_dev;
 static char buf[256];
 static char resp[1024];
+static char rp_buf[256];
 
 static int init(int argc, char **argv)
 {
@@ -51,9 +53,15 @@ static int init(int argc, char **argv)
         printf("Wrong UART device number - should be in range 0-%d.\n", UART_NUMOF - 1);
         return 1;
     }
-
+    at_dev_init_t at_init_params = {
-    int res = at_dev_init(&at_dev, UART_DEV(uart), baudrate, buf, sizeof(buf));
+        .baudrate = baudrate,
-
+        .rp_buf = rp_buf,
+        .rp_buf_size = sizeof(rp_buf),
+        .rx_buf = buf,
+        .rx_buf_size = sizeof(buf),
+        .uart = UART_DEV(uart),
+    };
+    int res = at_dev_init(&at_dev, &at_init_params);
     /* check the UART initialization return value and respond as needed */
     if (res == UART_NODEV) {
         puts("Invalid UART device given!");
@@ -110,7 +118,8 @@ static int send_lines(int argc, char **argv)
     }
 
     ssize_t len;
-    if ((len = at_send_cmd_get_lines(&at_dev, argv[1], resp, sizeof(resp), true, 10 * US_PER_SEC)) < 0) {
+    if ((len = at_send_cmd_get_lines(&at_dev, argv[1], resp, sizeof(resp),
+                                         true, 10 * US_PER_SEC)) < 0) {
         puts("Error");
         return 1;
     }
@@ -285,7 +294,7 @@ static int remove_urc(int argc, char **argv)
 }
 #endif
 
-static int sneaky_urc(int argc, char **argv)
+static int emulate_dce(int argc, char **argv)
 {
     (void)argc;
     (void)argv;
@@ -299,9 +308,21 @@ static int sneaky_urc(int argc, char **argv)
 #endif
 
     res = at_send_cmd_wait_ok(&at_dev, "AT+CFUN=1", US_PER_SEC);
-
     if (res) {
-        puts("Error AT+CFUN=1");
+        printf("%u: Error AT+CFUN=1: %d\n", __LINE__, res);
+        res = 1;
+        goto exit;
+    }
+
+    res = at_send_cmd(&at_dev, "AT+CFUN=1", US_PER_SEC);
+    if (res) {
+        printf("%u: Error AT+CFUN=1: %d\n", __LINE__, res);
+        res = 1;
+        goto exit;
+    }
+    res = at_wait_ok(&at_dev, US_PER_SEC);
+    if (res) {
+        printf("%u: Error AT+CFUN=1: %d\n", __LINE__, res);
         res = 1;
         goto exit;
     }
@@ -310,39 +331,72 @@ static int sneaky_urc(int argc, char **argv)
                                     "+CEREG:", resp_buf,
                                     sizeof(resp_buf), US_PER_SEC);
     if (res < 0) {
-        puts("Error AT+CEREG?");
+        printf("%u: Error AT+CEREG?: %d\n", __LINE__, res);
         res = 1;
         goto exit;
     }
 
     res = at_send_cmd_wait_prompt(&at_dev, "AT+USECMNG=0,0,\"cert\",128", US_PER_SEC);
     if (res) {
-        puts("Error AT+USECMNG");
+        printf("%u: Error AT+USECMNG: %d\n", __LINE__, res);
+        res =  1;
+        goto exit;
+    }
+
+    res = at_send_cmd_wait_prompt(&at_dev, "AT+PROMPTERROR", US_PER_SEC);
+    if (res != -AT_ERR_EXTENDED) {
+        printf("%u: Error AT+PROMPTERROR: %d\n", __LINE__, res);
+        res =  1;
+        goto exit;
+    }
+    res = atol(at_get_err_info(&at_dev));
+    if (res != 1984) {
+        printf("%u: Error AT+PROMPTERROR: %d\n", __LINE__, res);
         res =  1;
         goto exit;
     }
 
     res = at_send_cmd_wait_ok(&at_dev, "AT+CFUN=8", US_PER_SEC);
-
     if (res != -1) {
-        puts("Error AT+CFUN=8");
+        printf("%u: Error AT+CFUN=8: %d\n", __LINE__, res);
         res =  1;
         goto exit;
     }
 
     res = at_send_cmd_wait_ok(&at_dev, "AT+CFUN=9", US_PER_SEC);
-
+    if (res != -AT_ERR_EXTENDED) {
-    if (res != -2) {
+        printf("%u: Error AT+CFUN=9: %d\n", __LINE__, res);
-        puts("Error AT+CFUN=9");
         res =  1;
         goto exit;
     }
 
+    res = atol(at_get_err_info(&at_dev));
+    if (res != 666) {
+        printf("%u: Error AT+CFUN=9: %d\n", __LINE__, res);
+        res = 1;
+        goto exit;
+    }
+
+    res = at_send_cmd_get_lines(&at_dev, "AT+GETTWOLINES", resp_buf,
+                                sizeof(resp_buf), false, US_PER_SEC);
+    if (res < 0) {
+        printf("%u: Error AT+GETTWOLINES: %d\n", __LINE__, res);
+        res = 1;
+        goto exit;
+    }
+
+    if (strcmp(resp_buf, "first_line\nsecond_line\nOK")) {
+        printf("%u: Error AT+GETTWOLINES: response not matching\n", __LINE__);
+        res = 1;
+        goto exit;
+    }
+
     res = 0;
 exit:
 #ifdef MODULE_AT_URC
     at_remove_urc(&at_dev, &urc);
 #endif
+    printf("%s finished with %d\n", __func__, res);
     return res;
 }
 
@@ -357,7 +411,7 @@ static const shell_command_t shell_commands[] = {
     { "drain", "Drain AT device", drain },
     { "power_on", "Power on AT device", power_on },
     { "power_off", "Power off AT device", power_off },
-    { "sneaky_urc", "Test sneaky URC interference", sneaky_urc},
+    { "emulate_dce", "Test against the DCE emulation script.", emulate_dce},
 #ifdef MODULE_AT_URC
     { "add_urc", "Register an URC", add_urc },
     { "remove_urc", "De-register an URC", remove_urc },

tests/drivers/at/tests-with-config/emulate_dce.py

@@ -13,17 +13,27 @@
 #  1. Adapt the `EOL_IN`, `EOL_OUT`, `ECHO_ON` variables below to match your use case
 #  2. Run this script with the baud rate and the serial dev the device is connected
 #     to, e.g.:
-#       $ ./sneaky_urc 115200 /dev/ttyUSB0
+#       $ ./emulate_dce.py 115200 /dev/ttyUSB0
 #  4. run the test (e.g. make term)
 #  5. inside the test console:
 #    a) run the `init` command (e.g. init 0 115200)
-#    b) run `sneaky_urc` command
+#    b) run `emulate_dce` command
 #
 # If the command echoing is enabled, you will miss the URCs, but the commands
 # should work (e.g. the URC should not interfere with response parsing).
 #
 # If command echoing is enabled AND `MODULE_AT_URC` is defined, you should see
 # *some* of the URCs being parsed.
+#
+# The easiest way is to run this test on native, with an socat tty bridge:
+#   a) run `$ socat -d -d pty,raw,echo=0 pty,raw,echo=0`
+#      socat will display the pty endpoints it just created, e.g:
+#         2024/01/23 10:24:56 socat[45360] N PTY is /dev/pts/9
+#         2024/01/23 10:24:56 socat[45360] N PTY is /dev/pts/10
+#   b) pick one pty endpoint (e.g. /dev/pts/9) and run this script:
+#      `$ emulate_dce.py 115200 /dev/pts/9`
+#   c) pick the other endpoint and run the compiled binary
+#      ` $ ./bin/native/tests_at.elf -c /dev/pts/10 < tests-with-config/native_stdin`
 
 import sys
 import pexpect
@@ -37,17 +47,20 @@ EOL_IN = '\r'
 # EOL to send back to the device
 EOL_OUT = '\r\n'
 # Command echoing enabled
-ECHO_ON = False
+ECHO_ON = True
 
 CFUN_CMD = "AT+CFUN=1" + EOL_IN
 CFUN_ERR_CMD = "AT+CFUN=8" + EOL_IN
 CFUN_CME_CMD = "AT+CFUN=9" + EOL_IN
 CEREG_CMD = "AT+CEREG?" + EOL_IN
 USECMNG_CMD = "AT+USECMNG=0,0,\"cert\",128" + EOL_IN
+GETTWOLINES_CMD = "AT+GETTWOLINES" + EOL_IN
+PROMPTERROR_CMD = "AT+PROMPTERROR" + EOL_IN
 
 while True:
     try:
-        idx = tty.expect_exact([CFUN_CMD, CFUN_ERR_CMD, CFUN_CME_CMD, CEREG_CMD, USECMNG_CMD])
+        idx = tty.expect_exact([CFUN_CMD, CFUN_ERR_CMD, CFUN_CME_CMD, CEREG_CMD, USECMNG_CMD,
+                                GETTWOLINES_CMD, PROMPTERROR_CMD])
         if idx == 0:
             print(CFUN_CMD)
             tty.send(EOL_OUT + "+CSCON: 1" + EOL_OUT)
@@ -65,7 +78,7 @@ while True:
             tty.send(EOL_OUT + "+CSCON: 1" + EOL_OUT)
             if ECHO_ON:
                 tty.send(CFUN_CME_CMD)
-            tty.send(EOL_OUT + "+CME ERROR:" + EOL_OUT)
+            tty.send(EOL_OUT + "+CME ERROR: 666" + EOL_OUT)
         elif idx == 3:
             print(CEREG_CMD)
             tty.send(EOL_OUT + "+CSCON: 1" + EOL_OUT)
@@ -79,6 +92,16 @@ while True:
             if ECHO_ON:
                 tty.send(USECMNG_CMD)
             tty.send(">")
+        elif idx == 5:
+            print(GETTWOLINES_CMD)
+            if ECHO_ON:
+                tty.send(GETTWOLINES_CMD)
+            tty.send(EOL_OUT + "first_line" + EOL_OUT + "second_line" + EOL_OUT + "OK" + EOL_OUT)
+        elif idx == 6:
+            print(PROMPTERROR_CMD)
+            if ECHO_ON:
+                tty.send(PROMPTERROR_CMD)
+            tty.send(EOL_OUT + "+CME ERROR: 1984" + EOL_OUT)
     except pexpect.EOF:
         print("ERROR: EOF")
     except pexpect.TIMEOUT:

tests/drivers/at/tests-with-config/native_stdin

@@ -0,0 +1,2 @@
+init 0 115200
+emulate_dce