diff --git a/fpga/include/villas/fpga/ips/rtds.hpp b/fpga/include/villas/fpga/ips/rtds.hpp
index aff27601c..5f4b2e6fe 100644
--- a/fpga/include/villas/fpga/ips/rtds.hpp
+++ b/fpga/include/villas/fpga/ips/rtds.hpp
@@ -44,6 +44,14 @@ public:
 	std::list<std::string> getMemoryBlocks() const
 	{ return { registerMemory }; }
 
+	const StreamVertex&
+	getDefaultSlavePort() const
+	{ return getSlavePort(slavePort); }
+
+	const StreamVertex&
+	getDefaultMasterPort() const
+	{ return getMasterPort(masterPort); }
+
 private:
 	static constexpr const char registerMemory[] = "reg0";
 	static constexpr const char* irqTs = "irq_ts";
diff --git a/fpga/include/villas/fpga/ips/rtds2gpu.hpp b/fpga/include/villas/fpga/ips/rtds2gpu.hpp
index 64904d630..0b35848cf 100644
--- a/fpga/include/villas/fpga/ips/rtds2gpu.hpp
+++ b/fpga/include/villas/fpga/ips/rtds2gpu.hpp
@@ -27,9 +27,16 @@ public:
 
 	void dumpDoorbell(uint32_t doorbellRegister) const;
 
-	       static constexpr const char* registerMemory = "Reg";
+	bool doorbellIsValid(const uint32_t& doorbellRegister) const
+	{ return reinterpret_cast<const reg_doorbell_t&>(doorbellRegister).is_valid; }
+
+	void doorbellReset(uint32_t& doorbellRegister) const
+	{ doorbellRegister = 0; }
+
+	static constexpr const char* registerMemory = "Reg";
+
 	std::list<MemoryBlockName> getMemoryBlocks() const
-	       { return { registerMemory }; }
+	{ return { registerMemory }; }
 
 
 	const StreamVertex&
diff --git a/fpga/tests/rtds.cpp b/fpga/tests/rtds.cpp
index fd6de2baf..c60b70fb6 100644
--- a/fpga/tests/rtds.cpp
+++ b/fpga/tests/rtds.cpp
@@ -81,8 +81,12 @@ Test(fpga, rtds, .description = "RTDS")
 			auto dmaMaster = dma->getMasterPort(dma->mm2sPort);
 			auto dmaSlave = dma->getSlavePort(dma->s2mmPort);
 
-			rtds->connect(rtdsMaster, dmaSlave);
-			dma->connect(dmaMaster, rtdsSlave);
+//			rtds->connect(*rtds);
+//			logger->info("loopback");
+//			while(1);
+
+//			rtds->connect(rtdsMaster, dmaSlave);
+//			dma->connect(dmaMaster, rtdsSlave);
 
 			auto mem = villas::HostRam::getAllocator().allocate<int32_t>(0x100 / sizeof(int32_t));
 
diff --git a/fpga/tests/rtds2gpu.cpp b/fpga/tests/rtds2gpu.cpp
index b9ddd62af..a4c839bfc 100644
--- a/fpga/tests/rtds2gpu.cpp
+++ b/fpga/tests/rtds2gpu.cpp
@@ -31,15 +31,16 @@
 #include <villas/fpga/ips/gpu2rtds.hpp>
 #include <villas/fpga/ips/switch.hpp>
 #include <villas/fpga/ips/dma.hpp>
+#include <villas/fpga/ips/rtds.hpp>
 
 #include "global.hpp"
 
 
 static constexpr size_t SAMPLE_SIZE		= 4;
-static constexpr size_t SAMPLE_COUNT	= 8;
+static constexpr size_t SAMPLE_COUNT	= 1;
 static constexpr size_t FRAME_SIZE		= SAMPLE_COUNT * SAMPLE_SIZE;
 
-static constexpr size_t DOORBELL_OFFSET = SAMPLE_COUNT;
+static constexpr size_t DOORBELL_OFFSET = FRAME_SIZE;
 static constexpr size_t DATA_OFFSET = 0;
 
 static void dumpMem(const uint32_t* addr, size_t len)
@@ -86,11 +87,14 @@ Test(fpga, rtds2gpu, .description = "Rtds2Gpu")
 		auto gpu2rtds = dynamic_cast<villas::fpga::ip::Gpu2Rtds*>(
 		                     state.cards.front()->lookupIp(villas::fpga::Vlnv("acs.eonerc.rwth-aachen.de:hls:gpu2rtds:")));
 
+		auto rtds = dynamic_cast<villas::fpga::ip::Rtds*>(
+		                     state.cards.front()->lookupIp(villas::fpga::Vlnv("acs.eonerc.rwth-aachen.de:user:rtds_axis:")));
 
 
 		cr_assert_not_null(axiSwitch, "No AXI switch IP found");
 		cr_assert_not_null(dma, "No DMA IP found");
 		cr_assert_not_null(gpu2rtds, "No Gpu2Rtds IP found");
+		cr_assert_not_null(rtds, "RTDS IP not found");
 
 		rtds2gpu.dump(spdlog::level::debug);
 		gpu2rtds->dump(spdlog::level::debug);
@@ -166,3 +170,65 @@ Test(fpga, rtds2gpu, .description = "Rtds2Gpu")
 		logger->info(TXT_GREEN("Passed"));
 	}
 }
+
+Test(fpga, rtds2gpu_rtt_cpu, .description = "Rtds2Gpu RTT via CPU")
+{
+	auto logger = loggerGetOrCreate("unittest:rtds2gpu");
+
+	/* Collect neccessary IPs */
+
+	auto gpu2rtds = dynamic_cast<villas::fpga::ip::Gpu2Rtds*>(
+	                     state.cards.front()->lookupIp(villas::fpga::Vlnv("acs.eonerc.rwth-aachen.de:hls:gpu2rtds:")));
+
+	auto rtds2gpu = dynamic_cast<villas::fpga::ip::Rtds2Gpu*>(
+	                     state.cards.front()->lookupIp(villas::fpga::Vlnv("acs.eonerc.rwth-aachen.de:hls:rtds2gpu:")));
+
+	cr_assert_not_null(gpu2rtds, "No Gpu2Rtds IP found");
+	cr_assert_not_null(rtds2gpu, "No Rtds2Gpu IP not found");
+
+	for(auto& ip : state.cards.front()->ips) {
+		if(*ip != villas::fpga::Vlnv("acs.eonerc.rwth-aachen.de:user:rtds_axis:"))
+			continue;
+
+		auto& rtds = dynamic_cast<villas::fpga::ip::Rtds&>(*ip);
+		logger->info("Testing {}", rtds);
+
+		auto dmaRam = villas::HostDmaRam::getAllocator().allocate<uint32_t>(SAMPLE_COUNT + 1);
+		uint32_t* data = &dmaRam[DATA_OFFSET];
+		uint32_t* doorbell = &dmaRam[DOORBELL_OFFSET / SAMPLE_SIZE];
+
+		// TEST: rtds loopback via switch
+//		cr_assert(rtds.connect(rtds));
+//		logger->info("loopback");
+//		while(1);
+
+		cr_assert(rtds.connect(*rtds2gpu));
+		cr_assert(gpu2rtds->connect(rtds));
+
+
+		size_t count = 0;
+		while(true) {
+			rtds2gpu->doorbellReset(*doorbell);
+			rtds2gpu->startOnce(dmaRam.getMemoryBlock(), SAMPLE_COUNT, DATA_OFFSET, DOORBELL_OFFSET);
+
+			//			while(not rtds2gpu->isFinished());
+			while(not rtds2gpu->doorbellIsValid(*doorbell));
+
+//			rtds2gpu->dump();
+//			rtds2gpu->dumpDoorbell(data[1]);
+//			dumpMem(data, FRAME_SIZE + SAMPLE_SIZE);
+
+			// copy samples to gpu2rtds IP
+			for(size_t i = 0; i < SAMPLE_COUNT; i++) {
+				gpu2rtds->registerFrames[i] = data[i];
+			}
+
+			gpu2rtds->startOnce(SAMPLE_COUNT);
+//			while(not gpu2rtds->isFinished());
+
+
+			count++;
+//			logger->debug("Successful iterations {}, data {}", count, data[0]);
+		}
+	}
+}