diff --git a/examples/shell.rs b/examples/shell.rs
index 0e41ce1..030e008 100644
--- a/examples/shell.rs
+++ b/examples/shell.rs
@@ -73,6 +73,7 @@ use std::io::prelude::*;
 
 use embedded_sdmmc::{
     Error as EsError, RawDirectory, RawVolume, ShortFileName, VolumeIdx, VolumeManager,
+    VolumeOpenMode,
 };
 
 use crate::linux::{Clock, LinuxBlockDevice};
@@ -531,7 +532,10 @@ fn main() -> Result<(), Error> {
 
     let mut current_volume = None;
     for volume_no in 0..4 {
-        match ctx.volume_mgr.open_raw_volume(VolumeIdx(volume_no)) {
+        match ctx
+            .volume_mgr
+            .open_raw_volume(VolumeIdx(volume_no), VolumeOpenMode::ReadWrite)
+        {
             Ok(volume) => {
                 println!("Volume # {}: found", Context::volume_to_letter(volume_no));
                 match ctx.volume_mgr.open_root_dir(volume) {
diff --git a/src/lib.rs b/src/lib.rs
index aa98fb6..18b3ad1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -75,7 +75,7 @@ pub mod filesystem;
 pub mod sdcard;
 
 use filesystem::SearchId;
-use volume_mgr::VolumeOpenMode;
+pub use volume_mgr::VolumeOpenMode;
 
 #[doc(inline)]
 pub use crate::blockdevice::{Block, BlockCount, BlockDevice, BlockIdx};
diff --git a/src/volume_mgr.rs b/src/volume_mgr.rs
index 3f25568..aa21d85 100644
--- a/src/volume_mgr.rs
+++ b/src/volume_mgr.rs
@@ -18,9 +18,12 @@ use crate::{
 };
 use heapless::Vec;
 
+/// Opening volume mode
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub enum VolumeOpenMode {
+    /// Opening volume read only. This is faster than ReadWrite if only readings are done
     ReadOnly,
+    /// Opening volume for reading and writing.
     ReadWrite,
 }
 
diff --git a/tests/directories.rs b/tests/directories.rs
index df9154f..363d18a 100644
--- a/tests/directories.rs
+++ b/tests/directories.rs
@@ -1,6 +1,6 @@
 //! Directory related tests
 
-use embedded_sdmmc::{Mode, ShortFileName};
+use embedded_sdmmc::{Mode, ShortFileName, VolumeOpenMode};
 
 mod utils;
 
@@ -41,7 +41,7 @@ fn fat16_root_directory_listing() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
     let root_dir = volume_mgr
         .open_root_dir(fat16_volume)
@@ -103,7 +103,7 @@ fn fat16_sub_directory_listing() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
     let root_dir = volume_mgr
         .open_root_dir(fat16_volume)
@@ -168,7 +168,7 @@ fn fat32_root_directory_listing() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat32_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(1))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite)
         .expect("open volume 1");
     let root_dir = volume_mgr
         .open_root_dir(fat32_volume)
@@ -230,7 +230,7 @@ fn open_dir_twice() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat32_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(1))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite)
         .expect("open volume 1");
 
     let root_dir = volume_mgr
@@ -276,7 +276,7 @@ fn open_too_many_dirs() {
     > = embedded_sdmmc::VolumeManager::new_with_limits(disk, time_source, 0x1000_0000);
 
     let fat32_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(1))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite)
         .expect("open volume 1");
     let root_dir = volume_mgr
         .open_root_dir(fat32_volume)
@@ -295,7 +295,7 @@ fn find_dir_entry() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat32_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(1))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite)
         .expect("open volume 1");
 
     let root_dir = volume_mgr
@@ -325,7 +325,7 @@ fn delete_file() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat32_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(1))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite)
         .expect("open volume 1");
 
     let root_dir = volume_mgr
@@ -370,7 +370,7 @@ fn make_directory() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat32_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(1))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite)
         .expect("open volume 1");
 
     let root_dir = volume_mgr
diff --git a/tests/open_files.rs b/tests/open_files.rs
index dcdaadf..c4e14da 100644
--- a/tests/open_files.rs
+++ b/tests/open_files.rs
@@ -1,6 +1,6 @@
 //! File opening related tests
 
-use embedded_sdmmc::{Error, Mode, VolumeIdx, VolumeManager};
+use embedded_sdmmc::{Error, Mode, VolumeIdx, VolumeManager, VolumeOpenMode};
 
 mod utils;
 
@@ -11,7 +11,7 @@ fn open_files() {
     let mut volume_mgr: VolumeManager<utils::RamDisk<Vec<u8>>, utils::TestTimeSource, 4, 2, 1> =
         VolumeManager::new_with_limits(disk, time_source, 0xAA00_0000);
     let volume = volume_mgr
-        .open_raw_volume(VolumeIdx(0))
+        .open_raw_volume(VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume");
     let root_dir = volume_mgr.open_root_dir(volume).expect("open root dir");
 
diff --git a/tests/read_file.rs b/tests/read_file.rs
index b0e7628..3d2f92e 100644
--- a/tests/read_file.rs
+++ b/tests/read_file.rs
@@ -14,7 +14,7 @@ fn read_file_512_blocks() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
     let root_dir = volume_mgr
         .open_root_dir(fat16_volume)
@@ -56,7 +56,7 @@ fn read_file_all() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
     let root_dir = volume_mgr
         .open_root_dir(fat16_volume)
@@ -90,7 +90,7 @@ fn read_file_prime_blocks() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
     let root_dir = volume_mgr
         .open_root_dir(fat16_volume)
@@ -133,7 +133,7 @@ fn read_file_backwards() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
     let root_dir = volume_mgr
         .open_root_dir(fat16_volume)
diff --git a/tests/volume.rs b/tests/volume.rs
index 633a8d2..b3ec0cc 100644
--- a/tests/volume.rs
+++ b/tests/volume.rs
@@ -1,5 +1,7 @@
 //! Volume related tests
 
+use embedded_sdmmc::VolumeOpenMode;
+
 mod utils;
 
 #[test]
@@ -16,12 +18,12 @@ fn open_all_volumes() {
 
     // Open Volume 0
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
 
     // Fail to Open Volume 0 again
     assert!(matches!(
-        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(0)),
+        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite),
         Err(embedded_sdmmc::Error::VolumeAlreadyOpen)
     ));
 
@@ -29,23 +31,23 @@ fn open_all_volumes() {
 
     // Open Volume 1
     let fat32_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(1))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite)
         .expect("open volume 1");
 
     // Fail to Volume 1 again
     assert!(matches!(
-        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(1)),
+        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(1), VolumeOpenMode::ReadWrite),
         Err(embedded_sdmmc::Error::VolumeAlreadyOpen)
     ));
 
     // Open Volume 0 again
     let fat16_volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
 
     // Open any volume - too many volumes (0 and 1 are open)
     assert!(matches!(
-        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(0)),
+        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite),
         Err(embedded_sdmmc::Error::TooManyOpenVolumes)
     ));
 
@@ -54,13 +56,13 @@ fn open_all_volumes() {
 
     // This isn't a valid volume
     assert!(matches!(
-        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(2)),
+        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(2), VolumeOpenMode::ReadWrite),
         Err(embedded_sdmmc::Error::FormatError(_e))
     ));
 
     // This isn't a valid volume
     assert!(matches!(
-        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(9)),
+        volume_mgr.open_raw_volume(embedded_sdmmc::VolumeIdx(9), VolumeOpenMode::ReadWrite),
         Err(embedded_sdmmc::Error::NoSuchVolume)
     ));
 
@@ -79,7 +81,7 @@ fn close_volume_too_early() {
     let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
 
     let volume = volume_mgr
-        .open_raw_volume(embedded_sdmmc::VolumeIdx(0))
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadWrite)
         .expect("open volume 0");
     let root_dir = volume_mgr.open_root_dir(volume).expect("open root dir");
 
@@ -102,6 +104,40 @@ fn close_volume_too_early() {
     ));
 }
 
+#[test]
+fn volume_read_only_open_file_read_write() {
+    let time_source = utils::make_time_source();
+    let disk = utils::make_block_device(utils::DISK_SOURCE).unwrap();
+    let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
+
+    let volume = volume_mgr
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadOnly)
+        .expect("open volume 0");
+    let root_dir = volume_mgr.open_root_dir(volume).expect("open root dir");
+
+    // Dir open
+    assert!(matches!(
+        volume_mgr.open_file_in_dir(root_dir, "64MB.DAT", embedded_sdmmc::Mode::ReadWriteAppend),
+        Err(embedded_sdmmc::Error::VolumeReadOnly)
+    ));
+}
+
+#[test]
+fn volume_read_only_open_file_read_only() {
+    let time_source = utils::make_time_source();
+    let disk = utils::make_block_device(utils::DISK_SOURCE).unwrap();
+    let mut volume_mgr = embedded_sdmmc::VolumeManager::new(disk, time_source);
+
+    let volume = volume_mgr
+        .open_raw_volume(embedded_sdmmc::VolumeIdx(0), VolumeOpenMode::ReadOnly)
+        .expect("open volume 0");
+    let root_dir = volume_mgr.open_root_dir(volume).expect("open root dir");
+
+    volume_mgr
+        .open_file_in_dir(root_dir, "64MB.DAT", embedded_sdmmc::Mode::ReadOnly)
+        .unwrap();
+}
+
 // ****************************************************************************
 //
 // End Of File