hp-3478a: Check via GPIB serial poll if new data is available.

When just reading the data without check, the bus is blocked until new
data is available.

diff --git a/src/hardware/hp-3478a/protocol.c b/src/hardware/hp-3478a/protocol.c
index 3ddce5884aa1bddd72a199f4823bae3e2cde5f2c..6767bf0a03b4e7ff8b1b4b260c05a3fbe7abdc16 100644 (file)
--- a/src/hardware/hp-3478a/protocol.c
+++ b/src/hardware/hp-3478a/protocol.c
@@ -406,6 +406,7 @@ SR_PRIV int hp_3478a_receive_data(int fd, int revents, void *cb_data)
        struct sr_scpi_dev_inst *scpi;
        struct sr_dev_inst *sdi;
        struct dev_context *devc;
+       char status_register;
 
        (void)fd;
        (void)revents;
@@ -416,18 +417,28 @@ SR_PRIV int hp_3478a_receive_data(int fd, int revents, void *cb_data)
        scpi = sdi->conn;
 
        /*
-        * This is necessary to get the actual range for the encoding digits.
-        * When SPoll is implemmented, this can be done via SPoll.
+        * TODO: Wait for SRQ from the DMM when a new measurement is available.
+        *       For now, we don't wait for a SRQ, but just do a SPoll and
+        *       check the Data Ready bit (0x01).
+        *       This is necessary, because (1) reading a value will block the
+        *       bus until a measurement is available and (2) when switching
+        *       ranges, there could be a timeout.
         */
-       if (hp_3478a_get_status_bytes(sdi) != SR_OK)
+       if (sr_scpi_gpib_spoll(scpi, &status_register) != SR_OK)
+               return FALSE;
+       if (!(((uint8_t)status_register) & 0x01))
+               return TRUE;
+
+       /* Get a reading from the DMM. */
+       if (sr_scpi_get_double(scpi, NULL, &devc->measurement) != SR_OK)
                return FALSE;
 
        /*
-        * TODO: Implement GPIB-SPoll, to get notified by a SRQ when a new
-        *       measurement is available. This is necessary, because when
-        *       switching ranges, there could be a timeout.
+        * This is necessary to get the actual range for the encoding digits.
+        * Must be called after reading the value, because it resets the
+        * status register!
         */
-       if (sr_scpi_get_double(scpi, NULL, &devc->measurement) != SR_OK)
+       if (hp_3478a_get_status_bytes(sdi) != SR_OK)
                return FALSE;
 
        acq_send_measurement(sdi);

diff --git a/src/scpi.h b/src/scpi.h
index 13b2d3011d543149d80ad56cfb45fe1a0e290527..eeee9a553214048fa67ea17424654dbcd108c20b 100644 (file)
--- a/src/scpi.h
+++ b/src/scpi.h
@@ -163,4 +163,10 @@ SR_PRIV int sr_scpi_cmd_resp(const struct sr_dev_inst *sdi,
                int channel_command, const char *channel_name,
                GVariant **gvar, const GVariantType *gvtype, int command, ...);
 
+/*--- GPIB only functions ---------------------------------------------------*/
+
+#ifdef HAVE_LIBGPIB
+SR_PRIV int sr_scpi_gpib_spoll(struct sr_scpi_dev_inst *scpi, char *buf);
+#endif
+
 #endif

diff --git a/src/scpi/scpi_libgpib.c b/src/scpi/scpi_libgpib.c
index 2f3256be948e2eae404d02cda0e38b4391bab465..8f200e7d964ab247c41d727c56d0a43e8612bb99 100644 (file)
--- a/src/scpi/scpi_libgpib.c
+++ b/src/scpi/scpi_libgpib.c
@@ -155,6 +155,22 @@ static void scpi_gpib_free(void *priv)
        g_free(gscpi->name);
 }
 
+SR_PRIV int sr_scpi_gpib_spoll(struct sr_scpi_dev_inst *scpi, char *buf)
+{
+       struct scpi_gpib *gscpi = scpi->priv;
+
+       ibrsp(gscpi->descriptor, buf);
+
+       if (ibsta & ERR) {
+               sr_err("Error while serial polling: iberr = %s.",
+                       gpib_error_string(iberr));
+               return SR_ERR;
+       }
+       sr_spew("Successful serial poll: 0x%x", (uint8_t)buf[0]);
+
+       return SR_OK;
+}
+
 SR_PRIV const struct sr_scpi_dev_inst scpi_libgpib_dev = {
        .name = "GPIB",
        .prefix = "libgpib",