diff --git a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
index 7325b5c4cd..d6c96c52cb 100644
--- a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
+++ b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
@@ -546,7 +546,10 @@ void UARTDriver::write_pending_bytes_DMA(uint32_t n)
     if (tx_len == 0) {
         return;
     }
-    dma_handle->lock();
+    if (!dma_handle->lock_nonblock()) {
+        tx_len = 0;
+        return;
+    }
     tx_bounce_buf_ready = false;
     osalDbgAssert(txdma != nullptr, "UART TX DMA allocation failed");
     dmaStreamSetMemory0(txdma, tx_bounce_buf);
diff --git a/libraries/AP_HAL_ChibiOS/shared_dma.cpp b/libraries/AP_HAL_ChibiOS/shared_dma.cpp
index 65aa0c1eb0..9ef0f68447 100644
--- a/libraries/AP_HAL_ChibiOS/shared_dma.cpp
+++ b/libraries/AP_HAL_ChibiOS/shared_dma.cpp
@@ -58,14 +58,8 @@ void Shared_DMA::unregister()
 }
 
 // lock the DMA channels
-void Shared_DMA::lock(void)
+void Shared_DMA::lock_core(void)
 {
-    if (stream_id1 != SHARED_DMA_NONE) {
-        chBSemWait(&locks[stream_id1].semaphore);
-    }
-    if (stream_id2 != SHARED_DMA_NONE) {
-        chBSemWait(&locks[stream_id2].semaphore);
-    }
     // see if another driver has DMA allocated. If so, call their
     // deallocation function
     if (stream_id1 != SHARED_DMA_NONE &&
@@ -94,6 +88,38 @@ void Shared_DMA::lock(void)
     have_lock = true;
 }
 
+// lock the DMA channels, blocking method
+void Shared_DMA::lock(void)
+{
+    if (stream_id1 != SHARED_DMA_NONE) {
+        chBSemWait(&locks[stream_id1].semaphore);
+    }
+    if (stream_id2 != SHARED_DMA_NONE) {
+        chBSemWait(&locks[stream_id2].semaphore);
+    }
+    lock_core();
+}
+
+// lock the DMA channels, non-blocking
+bool Shared_DMA::lock_nonblock(void)
+{
+    if (stream_id1 != SHARED_DMA_NONE) {
+        if (chBSemWaitTimeout(&locks[stream_id1].semaphore, 1) != MSG_OK) {
+            return false;
+        }
+    }
+    if (stream_id2 != SHARED_DMA_NONE) {
+        if (chBSemWaitTimeout(&locks[stream_id2].semaphore, 1) != MSG_OK) {
+            if (stream_id1 != SHARED_DMA_NONE) {
+                chBSemSignal(&locks[stream_id1].semaphore);
+            }
+            return false;
+        }
+    }
+    lock_core();
+    return true;
+}
+
 // unlock the DMA channels
 void Shared_DMA::unlock(void)
 {
diff --git a/libraries/AP_HAL_ChibiOS/shared_dma.h b/libraries/AP_HAL_ChibiOS/shared_dma.h
index c9d73ba9a6..2d5d957cfd 100644
--- a/libraries/AP_HAL_ChibiOS/shared_dma.h
+++ b/libraries/AP_HAL_ChibiOS/shared_dma.h
@@ -41,6 +41,9 @@ public:
     // blocking lock call
     void lock(void);
 
+    // non-blocking lock call
+    bool lock_nonblock(void);
+    
     // unlock call. The DMA channel will not be immediately
     // deallocated. Instead it will be deallocated if another driver
     // needs it
@@ -65,6 +68,9 @@ private:
     uint8_t stream_id2;
     bool have_lock;
 
+    // core of lock call, after semaphores gained
+    void lock_core(void);
+    
     static struct dma_lock {
         // semaphore to ensure only one peripheral uses a DMA channel at a time
         binary_semaphore_t semaphore;