scpi: Fix incomplete data issue for e.g. Hameg HMO1024.

On a Hameg HMO1024 you get incomplete data because the USB transfer takes
longer than the scpi->read_timeout_ms of 1 second that is defined in
scpi_dev_inst_new(). Therefore reset the timeout in sr_scpi_get_string()
whenever the device sends a partial response.

diff --git a/src/scpi/scpi.c b/src/scpi/scpi.c
index 7604411384a9fcec385cffad37ec9b18673c37c7..ce3cb99d2362be792549d8e1970a76ebb1b35f57 100644 (file)
--- a/src/scpi/scpi.c
+++ b/src/scpi/scpi.c
@@ -383,7 +383,7 @@ SR_PRIV int sr_scpi_get_string(struct sr_scpi_dev_inst *scpi,
        char buf[256];
        int len;
        GString *response;
-       gint64 start;
+       gint64 laststart;
        unsigned int elapsed_ms;
 
        if (command)
@@ -393,7 +393,7 @@ SR_PRIV int sr_scpi_get_string(struct sr_scpi_dev_inst *scpi,
        if (sr_scpi_read_begin(scpi) != SR_OK)
                return SR_ERR;
 
-       start = g_get_monotonic_time();
+       laststart = g_get_monotonic_time();
 
        response = g_string_new("");
 
@@ -402,13 +402,15 @@ SR_PRIV int sr_scpi_get_string(struct sr_scpi_dev_inst *scpi,
        while (!sr_scpi_read_complete(scpi)) {
                len = sr_scpi_read_data(scpi, buf, sizeof(buf));
                if (len < 0) {
+                       sr_err("Incompletely read SCPI response.");
                        g_string_free(response, TRUE);
                        return SR_ERR;
+               } else if (len > 0) {
+                       laststart = g_get_monotonic_time();
                }
                g_string_append_len(response, buf, len);
-               elapsed_ms = (g_get_monotonic_time() - start) / 1000;
-               if (elapsed_ms >= scpi->read_timeout_ms)
-               {
+               elapsed_ms = (g_get_monotonic_time() - laststart) / 1000;
+               if (elapsed_ms >= scpi->read_timeout_ms) {
                        sr_err("Timed out waiting for SCPI response.");
                        g_string_free(response, TRUE);
                        return SR_ERR;
@@ -426,7 +428,7 @@ SR_PRIV int sr_scpi_get_string(struct sr_scpi_dev_inst *scpi,
        *scpi_response = response->str;
        g_string_free(response, FALSE);
 
-       sr_spew("Got response: '%.70s'.", *scpi_response);
+       sr_spew("Got response: '%.70s', length %d.", *scpi_response, strlen(*scpi_response));
 
        return SR_OK;
 }