ISSUE-232: Add JTAG APIs

This patch adds JTAG APIs for executing instructions and sending data directly
to devices over the JTAG scan chain.

Author: hkpeprah

pylink/jlink.py

@@ -2629,6 +2629,196 @@ def jtag_flush(self):
         """
         self._dll.JLINKARM_WriteBits()
 
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_store_instruction(self, instr, num_bits):
+        """Stores the specified JTAG instruction in the internal output buffer to
+        be written to the instruction register of the JTAG device.
+
+        The necessary bits to place the TAP controller into the Shift-IR state
+        are automatically added in order to form the complete command
+        sequence for the given instruction.
+
+        Data in the output buffer is not flushed until TDO data is required, or
+        ``jtag_sync_bits()`` or ``jtag_sync_bytes()`` is called.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+          instr (int): JTAG protocol command bits.
+          num_bits (int): Number of bits in the given instruction.
+
+        Returns:
+          Bit position in input buffer after instruction transmission.
+        """
+        buf = ctypes.c_uint8(instr)
+        return self._dll.JLINKARM_JTAG_StoreInst(ctypes.byref(buf), num_bits)
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_store_data(self, data, num_bits):
+        """Stores the specified JTAG data in the internal output buffer to be
+        written to the data register of the JTAG device.
+
+        The necessary bits to place the TAP controller into the Shift-DR state
+        are automatically added in order to form a complete data transmission.
+
+        Data in the output buffer is not flushed until TDO data is required, or
+        ``jtag_sync_bits()`` or ``jtag_sync_bytes()`` is called.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+          data (list): list of bits to transfer.
+          num_bits (int): number of bits to to transfer per integer in ``data``.
+
+        Returns:
+          Bit position in input buffer after instruction transmission.
+        """
+        buf = data
+        if isinstance(buf, list):
+            buf = bytes(buf)
+
+        return self._dll.JLINKARM_JTAG_StoreData(buf, len(data) * num_bits)
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_get_device_info(self, index=0):
+        """Retrieves the JTAG related information for the JTAG device on the scan chain.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+          index (int): index of the device on the scan chain.
+
+        Returns:
+          A ``JLinkJTAGDeviceInfo`` describing the requested device.
+
+        Raises:
+          ValueError: if index is less than 0 or >= number of devices on the scan chain.
+        """
+        if index < 0:
+            raise ValueError('Invalid index provided, must be > 0.')
+
+        info = structs.JLinkJTAGDeviceInfo()
+        res = self._dll.JLINKARM_JTAG_GetDeviceInfo(index, ctypes.byref(info))
+        if res == -1:
+            raise ValueError('Invalid index provided, no device found.')
+
+        info.DeviceId = self._dll.JLINKARM_JTAG_GetDeviceId(index)
+        return info
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_read(self, offset, num_bits):
+        """Reads the specified number of bits from the JTAG input buffer.
+
+        Note:
+          If there is data in the output buffer, then ``num_bits`` of data will
+          be transmitted.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+          offset (int): bit position within the input buffer to read from.
+          num_bits (int): total number of bits to read.
+
+        Returns:
+          List of bytes containing the TDO data. This function may return more
+          bytes than expected due to no context around the data size. The
+          caller should pull bits as appopriate starting from the first returned
+          byte.
+        """
+        # The smallest data length is 4 bits, so we use that as a divider. If
+        # the data length is actually 7 and the user specifies 7, we will
+        # return two integers, but that is fine, so the caller ultimately knows
+        # the data length they need.
+        buf_size = num_bits // 4
+        if (buf_size % 4) > 0:
+            buf_size += 1
+        buf = (ctypes.c_uint8 * buf_size)()
+        self._dll.JLINKARM_JTAG_GetData(ctypes.byref(buf), offset, num_bits)
+        return list(buf)
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_read8(self, offset):
+        """Reads a 8-bit integer from the JTAG input buffer.
+
+        Note:
+          If there is data in the output buffer, this function will force a
+          transmission.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+          offset (int): bit position within the input buffer to read from.
+
+        Returns:
+          The read 8-bit integer from the input buffer.
+        """
+        return self._dll.JLINKARM_JTAG_GetU8(offset)
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_read16(self, offset):
+        """Reads a 16-bit integer from the JTAG input buffer.
+
+        Note:
+          If there is data in the output buffer, this function will force a
+          transmission.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+          offset (int): bit position within the input buffer to read from.
+
+        Returns:
+          The read 16-bit integer from the input buffer.
+        """
+        return self._dll.JLINKARM_JTAG_GetU16(offset)
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_read32(self, offset):
+        """Reads a 32-bit integer from the JTAG input buffer.
+
+        Note:
+          If there is data in the output buffer, this function will force a
+          transmission.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+          offset (int): bit position within the input buffer to read from.
+
+        Returns:
+          The read 32-bit integer from the input buffer.
+        """
+        return self._dll.JLINKARM_JTAG_GetU32(offset)
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_sync_bits(self):
+        """Flushes the internal output buffer to the JTAG device.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+
+        Returns:
+          ``None``
+        """
+        self._dll.JLINKARM_JTAG_SyncBits()
+
+    @interface_required(enums.JLinkInterfaces.JTAG)
+    @open_required
+    def jtag_sync_bytes(self):
+        """Flushes the data content in the internal output buffer to the JTAG device.
+
+        This function will add the necessary bits to ensure the transmitted
+        data is byte-aligned.
+
+        Args:
+          self (JLink): the ``JLink`` instance.
+
+        Returns:
+          ``None``
+        """
+        self._dll.JLINKARM_JTAG_SyncBytes()
+
     @interface_required(enums.JLinkInterfaces.SWD)
     @connection_required
     def swd_read8(self, offset):

pylink/structs.py

@@ -1468,3 +1468,54 @@ def __str__(self):
           String formatted instance.
         """
         return '%s(SampleFreq=%uHz, MinDiv=%u)' % (self.__class__.__name__, self.BaseSampleFreq, self.MinDiv)
+
+
+class JLinkJTAGDeviceInfo(ctypes.Structure):
+    """Structure representing the information of a device on the JTAG scan chain.
+
+    Attributes:
+      sName: the name of the device.
+      IRLen: instruction register length.
+      IRPrint: instruction register print.
+      DeviceId: JTAG id.
+    """
+    _fields_ = [
+        ('sName', ctypes.c_char_p),
+        ('IRLen', ctypes.c_uint32),
+        ('IRPrint', ctypes.c_uint32),
+        ('DeviceId', ctypes.c_uint32)
+    ]
+
+    def __repr__(self):
+        """Returns a representation of this instance.
+
+        Args:
+          self (JLinkJTAGDeviceInfo): the ``JLinkJTAGDeviceInfo`` instance
+
+        Returns:
+          Returns a string representation of the instance.
+        """
+        return 'JLinkJTAGDeviceInfo(%s)' % self.__str__()
+
+    def __str__(self):
+        """Returns a string representation of this instance.
+
+        Args:
+          self (JLinkJTAGDeviceInfo): the ``JLinkJTAGDeviceInfo`` instance
+
+        Returns:
+          Returns a string specifying the device name and ID.
+        """
+        return '%s <Device Id. %s>' % (self.name, self.DeviceId)
+
+    @property
+    def name(self):
+        """Returns the name of the JTAG device.
+
+        Args:
+          self (JLinkJTAGDeviceInfo): the ``JLinkJTAGDeviceInfo`` instance
+
+        Returns:
+          Device name.
+        """
+        return ctypes.cast(self.sName, ctypes.c_char_p).value.decode()

tests/unit/test_jlink.py

@@ -3297,6 +3297,111 @@ def test_jlink_jtag_flush(self):
         self.jlink.jtag_flush()
         self.dll.JLINKARM_WriteBits.assert_called_once()
 
+    def test_jlijnk_jtag_store_instruction(self):
+        """Tests the J-Link JTAG method for storing a JTAG instruction.
+
+        Args:
+          self (TestJLink): the ``TestJLink`` instance
+
+        Returns:
+          ``None``
+        """
+        cmd = 0xE
+        self.jlink.jtag_store_instruction(cmd, 4)
+
+        c_byte, num_bits = self.dll.JLINKARM_JTAG_StoreInst.call_args[0]
+        self.assertEqual(4, num_bits)
+
+        c_uint = ctypes.cast(c_byte, ctypes.POINTER(ctypes.c_uint8)).contents
+        self.assertEqual(cmd, c_uint.value)
+
+    def test_jlink_jtag_store_data(self):
+        """Tests the J-Link JTAG method for storing TDI.
+
+        Args:
+          self (TestJLink): the ``TestJLink`` instance
+
+        Returns:
+          ``None``
+        """
+        tdi = [0xA, 0x3]
+        self.jlink.jtag_store_data(tdi, 5)
+
+        buf, num_bits = self.dll.JLINKARM_JTAG_StoreData.call_args[0]
+        self.assertEqual(10, num_bits)
+        self.assertEqual(b'\x0A\x03', bytearray(buf))
+
+    def test_jlink_jtag_get_device_info(self):
+        """Tests the J-Link JTAG method for retrieving JTAG device information.
+
+        Args:
+          self (TestJLink): the ``TestJLink`` instance
+
+        Return:
+          ``None``
+        """
+        with self.assertRaises(ValueError):
+            _ = self.jlink.jtag_get_device_info(-1)
+
+        self.dll.JLINKARM_JTAG_GetDeviceInfo.return_value = -1
+        with self.assertRaises(ValueError):
+            _ = self.jlink.jtag_get_device_info(0)
+
+        def _get_device_info(index, info):
+            c_info = ctypes.cast(info, ctypes.POINTER(structs.JLinkJTAGDeviceInfo)).contents
+            c_info.IRLen = 0x1
+            c_info.IRPrint = 0x2
+            c_info.DeviceId = 0x1337
+            name = b"Silk Song"
+            c_info.sName = ctypes.cast(name, ctypes.c_char_p)
+            return 0
+
+        self.dll.JLINKARM_JTAG_GetDeviceInfo = _get_device_info
+        self.dll.JLINKARM_JTAG_GetDeviceId.return_value = 0x1337
+
+        info = self.jlink.jtag_get_device_info(0)
+        self.assertEqual(0x1337, info.DeviceId)
+        self.assertEqual(0x1, info.IRLen)
+        self.assertEqual(0x2, info.IRPrint)
+        self.assertEqual("Silk Song", info.name)
+
+    def test_jlink_jtag_read(self):
+        """Tests the J-Link JTAG read methods.
+
+        Args:
+          self (TestJLink): the ``TestJLink`` instance
+
+        Returns:
+          ``None``
+        """
+        self.jlink._tif = enums.JLinkInterfaces.JTAG
+
+        val = 0x12345678
+        self.dll.JLINKARM_JTAG_GetU8.return_value = val & 0xFF
+        self.dll.JLINKARM_JTAG_GetU16.return_value = val & 0xFFFF
+        self.dll.JLINKARM_JTAG_GetU32.return_value = val & 0xFFFFFFFF
+
+        self.assertEqual(0x78, self.jlink.jtag_read8(0))
+        self.assertEqual(0x5678, self.jlink.jtag_read16(0))
+        self.assertEqual(0x12345678, self.jlink.jtag_read32(0))
+
+        def _get_data(buf, offset, num_bits):
+            c_buf = ctypes.cast(buf, ctypes.POINTER(ctypes.c_uint8))
+            buf_index = 0
+            bit_index = 0
+            while num_bits:
+                rd_size = min(num_bits, 4)
+                num_bits -= rd_size
+                b = 0
+                for i in range(0, rd_size):
+                    b |= ((val & (0x1 << bit_index)) >> bit_index) << i
+                    bit_index += 1
+                c_buf[buf_index] = b
+                buf_index += 1
+
+        self.dll.JLINKARM_JTAG_GetData = _get_data
+        self.assertEqual([0x8, 0x7, 0x6, 0x5], self.jlink.jtag_read(0, 16))
+
     def test_jlink_swd_read8(self):
         """Tests the J-Link ``swd_read8()`` method.