PR#44 (M): Fixed bug with live capture on real DSO-2250 hardware reports no waveform

HISTORY.md

@@ -427,3 +427,79 @@ Records key decisions, structural changes, and completed development stages.
   root cause remains open. Treated as a known, unresolved bug pending
   further hardware-side USB capture analysis.
 
+## 2026-09-07
+
+### Root cause found - DSO-2250 needs the extended 0x0b-0x0f command group
+
+- Correlated the Windows reference-driver capture against the application's
+  own USB capture with `tshark` and found the application implements only the
+  DSO-2090 command set (`0x00`-`0x07`), while the DSO-2250 requires the
+  extended acquisition-configuration commands `0x0b`-`0x0f`. The DSO-2090
+  `SetTriggerAndSampleRate` command (`0x01`) is silently ignored by the
+  DSO-2250, so the capture engine never arms and `GetCaptureState` stays in
+  its power-on state forever.
+- Bulk-OUT command comparison (reference vs application): `0x01` sent 0 vs 2
+  (the ignored 2090 command), `0x05` GetData 237 vs 0 (analog data never
+  read), `0x09` GetLogicalData 78 vs 0, and each of `0x0b`-`0x0f` 78 vs 0
+  (the arming group is entirely absent from the application).
+
+### Recorded - full DSO-2250 bulk-command semantics from OpenHantek
+
+- Documented the DSO-2250 bulk-command semantics decoded from the OpenHantek
+  project (`hantekprotocol/bulkcode.h`) for future protocol work:
+  - `0x00` SetFilter, `0x01` SetTriggerAndSampleRate (DSO-2090 only, ignored
+    by the DSO-2250), `0x02` ForceTrigger, `0x03` StartSampling, `0x04`
+    EnableTrigger, `0x05` GetData, `0x06` GetCaptureState, `0x07` SetGain.
+  - `0x08` SetLogicalData, `0x09` GetLogicalData, `0x0a` unknown.
+  - `0x0b` BSetChannels - enabled-channel selection, `[0b][00][channels][00]`.
+  - `0x0c` CSetTriggerOrSampleRate - trigger source/bits,
+    `[0c][00][triggerBits][00]...`.
+  - `0x0d` DSetBuffer - record-length id, `[0d][00][recordLenId][00]`.
+  - `0x0e` ESetTriggerOrSampleRate - sample-rate bits,
+    `[0e][00][srBits][00][sr0][sr1][00][00]`.
+  - `0x0f` FSetBuffer - trigger position, `[0f][00][postTrig0-2][00]`
+    `[preTrig0-2][00][00][00]`.
+  - Completed-capture state value for the DSO-2250 is `3`
+    (`CAPTURE_READY2250`).
+- Recorded the known-good reference configuration bytes captured immediately
+  before the first successful capture, for the arming group used below:
+  `0x0c` `0c 0f 02 00 02 00 00 00`, `0x0b` `0b 0f 00 00`, `0x0d`
+  `0d 0f 01 00`, `0x0e` `0e 00 01 00 00 00 00 00`, `0x0f`
+  `0f 00 fe d7 07 00 fe ff 07 00 00 00`, sent in the order
+  `0c, 0b, 0d, 0e, 0f`.
+
+### Stage 4 - Send the DSO-2250 acquisition-configuration command group
+
+- Replaced both DSO-2090 `SetTriggerAndSampleRate` (`0x01`) sends in
+  `configureCapture()` with a new `configureDso2250Timebase()` helper that
+  issues the extended arming group `0x0c, 0x0b, 0x0d, 0x0e, 0x0f` using the
+  known-good reference bytes, reusing the existing begin-command/speed-check
+  bulk framing.
+- Prepended `0x09` GetLogicalData to the arming group and drained the single
+  512-byte bulk-IN (`0x86`) response it returns, mirroring the reference
+  driver, so the logic/auto-range subsystem is initialised the same way
+  before analog capture.
+- Removed the now-unused DSO-2090 timebase constants and added the DSO-2250
+  command payloads as named constants.
+- Kept the calibration-derived `SetOffset` (`0xB4`) write, relay
+  (`0xB5`) configuration, and calibration reads (`0xA2`) unchanged.
+
+### Stage 4 - Corrected the capture read size and confirmed the data path
+
+- Verified on hardware that the arming group works: the acquisition error
+  changed from silent no-waveform to `USB timeout while reading channel
+  data`, proving the capture engine now reaches `captureCompleteState` (```3```)
+  and accepts the `0x05` GetData command.
+- Measured the true capture size from the reference dump with `tshark`: one
+  capture is 40 bulk-IN (`0x86`) packets of 512 bytes = 20480 bytes = 10240
+  samples per channel (two channels interleaved), selected by record-length
+  id `1` (`0x0d 0f 01 00`). The profile declared `sampleCount = 32768`, so
+  the application requested 128 packets, received 40, and blocked on the
+  41st packet until the read timed out.
+- Corrected `sampleCount` from `32768` to `10240` in both DSO-2250 USB
+  profiles (bootloader and operational) in `usb/src/usb_device.cpp`; the
+  fixed sample and packet buffers accommodate the smaller size unchanged.
+- Confirmed on hardware: the oscilloscope now returns valid waveform data
+  over USB. On-screen rendering is not yet implemented, so Stage 4 remains
+  open until the captured samples are drawn.
+

capture/src/acquisition_loop.cpp

@@ -70,15 +70,43 @@ static const unsigned int kForceRestartThreshold = 3U;
  */
 static const uint8_t kDefaultVoltageRangeCode = 0U;    /**< VOLTAGE_5V */
 static const uint8_t kDefaultCouplingDc = 0U;          /**< COUPLING_AC */
-static const uint8_t kDefaultSelectedChannel = 2U;     /**< SELECT_CH1CH2 */
-static const uint8_t kDefaultTriggerSource = 1U;       /**< TRIGGER_CH1 */
-static const uint8_t kDefaultTriggerSlope = 0U;        /**< SLOPE_POSITIVE */
-static const uint8_t kDefaultSampleSizeCode = 2U;      /**< BUFFER_LARGE */
-static const uint16_t kDefaultTimeBaseValue = 0xFFF7U; /**< TIME_1ms preset */
-/** 1ms/div is past the fast range */
-static const uint8_t kDefaultTimeBaseFastCode = 4U;
-/** No-offset trigger position */
-static const uint32_t kDefaultTriggerPosition = 0x77660U;
+
+/**
+ * @brief DSO-2250 acquisition-configuration command group (0x0b-0x0f)
+ * @details The DSO-2090 setTriggerNSampleRate command (0x01) does NOT arm
+ * the DSO-2250 capture engine. This model needs the extended command group
+ * 0x0b-0x0f - set channels, trigger source, record length, sample rate and
+ * trigger position. Without it GetCaptureState never leaves its power-on
+ * state and no waveform is ever returned. The byte values below reproduce
+ * the known-good sequence captured from the vendor Windows driver (see
+ * WorkingDocs USB captures): both channels, internal CH1 trigger, large
+ * record buffer and a centered trigger position. TEMPORARY fixed
+ * configuration until Stage 5 wires the Timebase/Scale/Trigger UI controls.
+ */
+static const uint8_t kDso2250SetTriggerSource[8] = {
+    0x0CU, 0x0FU, 0x02U, 0x00U, 0x02U, 0x00U, 0x00U, 0x00U
+};
+/** Channel-enable command: both channels active */
+static const uint8_t kDso2250SetChannels[4] = {
+    0x0BU, 0x0FU, 0x00U, 0x00U
+};
+/** Record-length command: large capture buffer */
+static const uint8_t kDso2250SetRecordLength[4] = {
+    0x0DU, 0x0FU, 0x01U, 0x00U
+};
+/** Sample-rate command: default acquisition rate */
+static const uint8_t kDso2250SetSampleRate[8] = {
+    0x0EU, 0x00U, 0x01U, 0x00U, 0x00U, 0x00U, 0x00U, 0x00U
+};
+/** Trigger-position command: centered post/pre-trigger window */
+static const uint8_t kDso2250SetTriggerPosition[12] = {
+    0x0FU, 0x00U, 0xFEU, 0xD7U, 0x07U, 0x00U,
+    0xFEU, 0xFFU, 0x07U, 0x00U, 0x00U, 0x00U
+};
+/** GetLogicalData command: primes the logic/auto-range subsystem */
+static const uint8_t kDso2250GetLogicalData[2] = {
+    0x09U, 0x00U
+};
 
 /**
  * @brief Channel/trigger offset DAC configuration sent once before the
@@ -158,6 +186,22 @@ static usb::SUsbTransferResult configureCapture(
     EAcquisitionOperation *failedOperation
 );
 
+/**
+ * @brief Sends the DSO-2250 acquisition-configuration command group
+ * @details Primes the logic/auto-range subsystem with GetLogicalData
+ * (0x09), draining its bulk-IN response, then issues the extended commands
+ * 0x0b-0x0f that arm the DSO-2250 capture engine (channels, trigger source,
+ * record length, sample rate, trigger position). Replaces the DSO-2090
+ * setTriggerNSampleRate (0x01) command, which the DSO-2250 ignores.
+ * @param[in] connection USB connection to configure
+ * @param[out] failedOperation First operation that failed
+ * @returns Result of the first failed operation or the final successful write
+ */
+static usb::SUsbTransferResult configureDso2250Timebase(
+    const usb::SUsbConnection &connection,
+    EAcquisitionOperation *failedOperation
+);
+
 /**
  * @brief Computes the centered offset DAC byte for one channel
  * @param[in] channelLevels Calibration table read via the channel-level
@@ -612,6 +656,84 @@ static uint8_t channelLevelCenterByte(
 
 /*----------------------------------------------------------------------------*/
 
+/** @fn configureDso2250Timebase */
+static usb::SUsbTransferResult configureDso2250Timebase(
+    const usb::SUsbConnection &connection,
+    EAcquisitionOperation *failedOperation
+) {
+    struct SConfigCommand {
+        const uint8_t *payload; /**< Command bytes */
+        int length;             /**< Number of command bytes */
+    };
+    const SConfigCommand commands[5] = {
+        {
+            kDso2250SetTriggerSource,
+            static_cast<int>(sizeof(kDso2250SetTriggerSource))
+        },
+        {
+            kDso2250SetChannels,
+            static_cast<int>(sizeof(kDso2250SetChannels))
+        },
+        {
+            kDso2250SetRecordLength,
+            static_cast<int>(sizeof(kDso2250SetRecordLength))
+        },
+        {
+            kDso2250SetSampleRate,
+            static_cast<int>(sizeof(kDso2250SetSampleRate))
+        },
+        {
+            kDso2250SetTriggerPosition,
+            static_cast<int>(sizeof(kDso2250SetTriggerPosition))
+        }
+    };
+    uint8_t logicalData[kRawUsbPacketMaxSize];
+    usb::SUsbTransferResult result = {
+        usb::EUsbTransferStatus::eSuccess, 0, ""
+    };
+    size_t index = 0U;
+
+    /* GetLogicalData (0x09) primes the logic/auto-range subsystem and
+       returns one bulk-IN packet that the vendor driver drains before the
+       analog arming group; the payload itself is unused here. */
+    result = executeCommand(
+        connection,
+        kDso2250GetLogicalData,
+        static_cast<int>(sizeof(kDso2250GetLogicalData)),
+        EAcquisitionOperation::eSetTriggerNSampleRateCmd,
+        failedOperation
+    );
+    if (result.status == usb::EUsbTransferStatus::eSuccess) {
+        *failedOperation = EAcquisitionOperation::eSetTriggerNSampleRateCmd;
+        result = usb::bulkRead(
+            connection,
+            connection.captureProtocol.bulkInEndpoint,
+            logicalData,
+            connection.captureProtocol.bulkInPacketLength,
+            kTransferTimeoutMs,
+            kTransferAttempts,
+            connection.captureProtocol.bulkInPacketLength
+        );
+    }
+
+    for (index = 0U;
+         (index < 5U) &&
+         (result.status == usb::EUsbTransferStatus::eSuccess);
+         ++index) {
+        result = executeCommand(
+            connection,
+            commands[index].payload,
+            commands[index].length,
+            EAcquisitionOperation::eSetTriggerNSampleRateCmd,
+            failedOperation
+        );
+    }
+
+    return result;
+}
+
+/*----------------------------------------------------------------------------*/
+
 /** @fn configureCapture */
 static usb::SUsbTransferResult configureCapture(
     const usb::SUsbConnection &connection,
@@ -621,25 +743,6 @@ static usb::SUsbTransferResult configureCapture(
         connection.captureProtocol.setFilterCmd, 0x0FU,
         0U, 0U, 0U, 0U, 0U, 0U
     };
-    const uint8_t tsrByte1 = static_cast<uint8_t>(
-        kDefaultTriggerSource |
-        (kDefaultSampleSizeCode << 2U) |
-        (kDefaultTimeBaseFastCode << 5U)
-    );
-    const uint8_t tsrByte2 = static_cast<uint8_t>(
-        kDefaultSelectedChannel | (kDefaultTriggerSlope << 3U)
-    );
-    const uint8_t triggerNSampleRateCmd[12] = {
-        connection.captureProtocol.setTriggerNSampleRateCmd, 0U,
-        tsrByte1, tsrByte2,
-        static_cast<uint8_t>(kDefaultTimeBaseValue),
-        static_cast<uint8_t>(kDefaultTimeBaseValue >> 8U),
-        static_cast<uint8_t>(kDefaultTriggerPosition),
-        static_cast<uint8_t>(kDefaultTriggerPosition >> 8U),
-        0U, 0U,
-        static_cast<uint8_t>(kDefaultTriggerPosition >> 16U),
-        0U
-    };
     const uint8_t voltageByte = static_cast<uint8_t>(
         (2U - (kDefaultVoltageRangeCode % 3U)) |
         ((2U - (kDefaultVoltageRangeCode % 3U)) << 2U) |
@@ -684,13 +787,7 @@ static usb::SUsbTransferResult configureCapture(
         failedOperation
     );
     if (result.status == usb::EUsbTransferStatus::eSuccess) {
-        result = executeCommand(
-            connection,
-            triggerNSampleRateCmd,
-            sizeof(triggerNSampleRateCmd),
-            EAcquisitionOperation::eSetTriggerNSampleRateCmd,
-            failedOperation
-        );
+        result = configureDso2250Timebase(connection, failedOperation);
     }
     if (result.status == usb::EUsbTransferStatus::eSuccess) {
         result = executeCommand(
@@ -744,13 +841,7 @@ static usb::SUsbTransferResult configureCapture(
         );
     }
     if (result.status == usb::EUsbTransferStatus::eSuccess) {
-        result = executeCommand(
-            connection,
-            triggerNSampleRateCmd,
-            sizeof(triggerNSampleRateCmd),
-            EAcquisitionOperation::eSetTriggerNSampleRateCmd,
-            failedOperation
-        );
+        result = configureDso2250Timebase(connection, failedOperation);
     }
     if (result.status == usb::EUsbTransferStatus::eSuccess) {
         *failedOperation = EAcquisitionOperation::eNone;

usb/src/usb_device.cpp

@@ -60,14 +60,14 @@ static const SSupportedDevice kSupportedDevices[] = {
     /* The bootloader exposes the bulk pair on alt setting 1. */
     {
         "Hantek DSO-2250 Bootloader", "DSO2250",
-        { 32768U, 512U, 0x02U, 0x86U, 2U, true, 3U, 6U, 5U, 3U, 4U, 2U, 0U, 1U,
+        { 10240U, 512U, 0x02U, 0x86U, 2U, true, 3U, 6U, 5U, 3U, 4U, 2U, 0U, 1U,
           7U, 0xB5U, 0xA2U, 0xB4U },
         core::EInstrumentModel::eHantekDso2250,
         0x04B4U, 0x2250U, 0x04B5U, 0U, 1U, true
     },
     {
         "Hantek DSO-2250", "DSO2250",
-        { 32768U, 512U, 0x02U, 0x86U, 2U, true, 3U, 6U, 5U, 3U, 4U, 2U, 0U, 1U,
+        { 10240U, 512U, 0x02U, 0x86U, 2U, true, 3U, 6U, 5U, 3U, 4U, 2U, 0U, 1U,
           7U, 0xB5U, 0xA2U, 0xB4U },
         core::EInstrumentModel::eHantekDso2250,
         0x04B5U, 0x2250U, 0x04B5U, 0U, 0U, false