diff --git a/lib/pbio/drv/uart/uart_ev3.c b/lib/pbio/drv/uart/uart_ev3.c
index adedc316c..e0dedf002 100644
--- a/lib/pbio/drv/uart/uart_ev3.c
+++ b/lib/pbio/drv/uart/uart_ev3.c
@@ -58,15 +58,15 @@ struct _pbdrv_uart_dev_t {
     /** The buffer passed to the read function. */
     uint8_t *read_buf;
     /** The length of read_buf in bytes. */
-    uint8_t read_length;
+    uint32_t read_length;
     /** The current position in read_buf. */
-    uint8_t read_pos;
+    uint32_t read_pos;
     /** The buffer passed to the write function. */
     const uint8_t *write_buf;
     /** The length of write_buf in bytes. */
-    uint8_t write_length;
+    uint32_t write_length;
     /** The current position in write_buf. */
-    volatile uint8_t write_pos;
+    volatile uint32_t write_pos;
 };
 
 static pbdrv_uart_dev_t uart_devs[PBDRV_CONFIG_UART_EV3_NUM_UART];
@@ -89,7 +89,7 @@ int32_t pbdrv_uart_get_char(pbdrv_uart_dev_t *uart) {
     return ringbuf_get(&uart->rx_buf);
 }
 
-pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -131,7 +131,7 @@ pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uin
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-static pbio_error_t pbdrv_uart_write_pru(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint8_t length, uint32_t timeout) {
+static pbio_error_t pbdrv_uart_write_pru(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     const pbdrv_uart_ev3_platform_data_t *pdata = uart->pdata;
 
@@ -178,7 +178,7 @@ static pbio_error_t pbdrv_uart_write_pru(pbio_os_state_t *state, pbdrv_uart_dev_
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_uart_write_hw(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_write_hw(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     const pbdrv_uart_ev3_platform_data_t *pdata = uart->pdata;
 
@@ -240,7 +240,7 @@ pbio_error_t pbdrv_uart_write_hw(pbio_os_state_t *state, pbdrv_uart_dev_t *uart,
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint32_t length, uint32_t timeout) {
     const pbdrv_uart_ev3_platform_data_t *pdata = uart->pdata;
 
     if (pdata->uart_kind == EV3_UART_HW) {
diff --git a/lib/pbio/drv/uart/uart_stm32f0.c b/lib/pbio/drv/uart/uart_stm32f0.c
index 12b9f5d80..2e8adcf7e 100644
--- a/lib/pbio/drv/uart/uart_stm32f0.c
+++ b/lib/pbio/drv/uart/uart_stm32f0.c
@@ -33,11 +33,11 @@ struct _pbdrv_uart_dev_t {
     volatile uint8_t rx_ring_buf_head;
     uint8_t rx_ring_buf_tail;
     uint8_t *rx_buf;
-    uint8_t rx_buf_size;
-    uint8_t rx_buf_index;
+    uint32_t rx_buf_size;
+    uint32_t rx_buf_index;
     const uint8_t *tx_buf;
-    uint8_t tx_buf_size;
-    uint8_t tx_buf_index;
+    uint32_t tx_buf_size;
+    uint32_t tx_buf_index;
     pbio_os_timer_t rx_timer;
     pbio_os_timer_t tx_timer;
     uint8_t irq;
@@ -59,7 +59,7 @@ pbio_error_t pbdrv_uart_get_instance(uint8_t id, pbdrv_uart_dev_t **uart_dev) {
     return PBIO_SUCCESS;
 }
 
-pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -102,7 +102,7 @@ pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uin
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
diff --git a/lib/pbio/drv/uart/uart_stm32f4_ll_irq.c b/lib/pbio/drv/uart/uart_stm32f4_ll_irq.c
index f52720817..ba50addf4 100644
--- a/lib/pbio/drv/uart/uart_stm32f4_ll_irq.c
+++ b/lib/pbio/drv/uart/uart_stm32f4_ll_irq.c
@@ -39,15 +39,15 @@ struct _pbdrv_uart_dev_t {
     /** The buffer of the ongoing async read function. */
     uint8_t *read_buf;
     /** The length of read_buf in bytes. */
-    uint8_t read_length;
+    uint32_t read_length;
     /** The current position in read_buf. */
-    uint8_t read_pos;
+    uint32_t read_pos;
     /** The buffer of the ongoing write function. */
     const uint8_t *write_buf;
     /** The length of write_buf in bytes. */
-    uint8_t write_length;
+    uint32_t write_length;
     /** The current position in write_buf. */
-    volatile uint8_t write_pos;
+    volatile uint32_t write_pos;
 };
 
 static pbdrv_uart_dev_t uart_devs[PBDRV_CONFIG_UART_STM32F4_LL_IRQ_NUM_UART];
@@ -66,7 +66,7 @@ pbio_error_t pbdrv_uart_get_instance(uint8_t id, pbdrv_uart_dev_t **uart_dev) {
     return PBIO_SUCCESS;
 }
 
-pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -108,7 +108,7 @@ pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uin
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
diff --git a/lib/pbio/drv/uart/uart_stm32l4_ll_dma.c b/lib/pbio/drv/uart/uart_stm32l4_ll_dma.c
index d9fbf4050..b1f569a93 100644
--- a/lib/pbio/drv/uart/uart_stm32l4_ll_dma.c
+++ b/lib/pbio/drv/uart/uart_stm32l4_ll_dma.c
@@ -34,9 +34,9 @@ struct _pbdrv_uart_dev_t {
     pbio_os_timer_t rx_timer;
     pbio_os_timer_t tx_timer;
     volatile uint8_t *rx_data;
-    uint8_t rx_tail;
+    uint32_t rx_tail;
     uint8_t *read_buf;
-    uint8_t read_length;
+    uint32_t read_length;
 };
 
 static pbdrv_uart_dev_t uart_devs[PBDRV_CONFIG_UART_STM32L4_LL_DMA_NUM_UART];
@@ -55,8 +55,8 @@ pbio_error_t pbdrv_uart_get_instance(uint8_t id, pbdrv_uart_dev_t **uart_dev) {
     return PBIO_SUCCESS;
 }
 
-static void volatile_copy(volatile uint8_t *src, uint8_t *dst, uint8_t size) {
-    for (int i = 0; i < size; i++) {
+static void volatile_copy(volatile uint8_t *src, uint8_t *dst, uint32_t size) {
+    for (uint32_t i = 0; i < size; i++) {
         dst[i] = src[i];
     }
 }
@@ -187,7 +187,7 @@ static uint32_t pbdrv_uart_get_num_available(pbdrv_uart_dev_t *uart) {
     return (rx_head - uart->rx_tail) & (RX_DATA_SIZE - 1);
 }
 
-pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -227,7 +227,7 @@ pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, uin
     PBIO_OS_ASYNC_END(PBIO_SUCCESS);
 }
 
-pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     const pbdrv_uart_stm32l4_ll_dma_platform_data_t *pdata = uart->pdata;
 
diff --git a/lib/pbio/include/pbdrv/uart.h b/lib/pbio/include/pbdrv/uart.h
index 581bed46a..42e349893 100644
--- a/lib/pbio/include/pbdrv/uart.h
+++ b/lib/pbio/include/pbdrv/uart.h
@@ -45,7 +45,7 @@ int32_t pbdrv_uart_get_char(pbdrv_uart_dev_t *uart_dev);
  * @param [in]  timeout   The timeout in milliseconds or 0 for no timeout.
  * @return The error code.
  */
-pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint8_t length, uint32_t timeout);
+pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint32_t length, uint32_t timeout);
 
 /**
  * Asynchronously write to the UART.
@@ -58,7 +58,7 @@ pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev,
  *
  * @return The error code.
  */
-pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint8_t length, uint32_t timeout);
+pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart, const uint8_t *msg, uint32_t length, uint32_t timeout);
 
 #else // PBDRV_CONFIG_UART
 
@@ -70,13 +70,13 @@ static inline void pbdrv_uart_set_baud_rate(pbdrv_uart_dev_t *uart_dev, uint32_t
 }
 static inline void pbdrv_uart_stop(pbdrv_uart_dev_t *uart_dev) {
 }
-static inline pbio_error_t pbdrv_uart_read_begin(pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint8_t length, uint32_t timeout) {
+static inline pbio_error_t pbdrv_uart_read_begin(pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint32_t length, uint32_t timeout) {
     return PBIO_ERROR_NOT_SUPPORTED;
 }
 static inline pbio_error_t pbdrv_uart_read_end(pbdrv_uart_dev_t *uart_dev) {
     return PBIO_ERROR_NOT_SUPPORTED;
 }
-static inline pbio_error_t pbdrv_uart_write_begin(pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint8_t length, uint32_t timeout) {
+static inline pbio_error_t pbdrv_uart_write_begin(pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint32_t length, uint32_t timeout) {
     return PBIO_ERROR_NOT_SUPPORTED;
 }
 static inline pbio_error_t pbdrv_uart_write_end(pbdrv_uart_dev_t *uart_dev) {
@@ -97,11 +97,11 @@ static inline int32_t pbdrv_uart_get_char(pbdrv_uart_dev_t *uart_dev) {
     return -1;
 }
 
-static inline pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint8_t length, uint32_t timeout) {
+static inline pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint32_t length, uint32_t timeout) {
     return PBIO_ERROR_NOT_SUPPORTED;
 }
 
-static inline pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint8_t length, uint32_t timeout) {
+static inline pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint32_t length, uint32_t timeout) {
     return PBIO_ERROR_NOT_SUPPORTED;
 }
 
diff --git a/lib/pbio/src/port_lump.c b/lib/pbio/src/port_lump.c
index cba71058e..077828928 100644
--- a/lib/pbio/src/port_lump.c
+++ b/lib/pbio/src/port_lump.c
@@ -169,9 +169,9 @@ struct _pbio_port_lump_dev_t {
     /** New baud rate that will be set with ev3_uart_change_bitrate. */
     uint32_t new_baud_rate;
     /** Size of the current message being transmitted. */
-    uint8_t tx_msg_size;
+    uint32_t tx_msg_size;
     /** Size of the current message being received. */
-    uint8_t rx_msg_size;
+    uint32_t rx_msg_size;
     /** Total number of errors that have occurred. */
     uint32_t err_count;
     /** Flag that indicates that good DATA lump_dev->msg has been received since last watchdog timeout. */
diff --git a/lib/pbio/test/src/test_lump.c b/lib/pbio/test/src/test_lump.c
index 2b98873e5..71d688689 100644
--- a/lib/pbio/test/src/test_lump.c
+++ b/lib/pbio/test/src/test_lump.c
@@ -1110,7 +1110,7 @@ void pbdrv_uart_init(void) {
 void pbdrv_uart_stop(pbdrv_uart_dev_t *uart_dev) {
 }
 
-pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);
 
@@ -1134,7 +1134,7 @@ pbio_error_t pbdrv_uart_read(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev,
     PBIO_OS_ASYNC_END(uart_dev->rx_msg_result);
 }
 
-pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, const uint8_t *msg, uint8_t length, uint32_t timeout) {
+pbio_error_t pbdrv_uart_write(pbio_os_state_t *state, pbdrv_uart_dev_t *uart_dev, const uint8_t *msg, uint32_t length, uint32_t timeout) {
 
     PBIO_OS_ASYNC_BEGIN(state);