From 7dbaa01256970e57980cf700fa9c6df6843310b9 Mon Sep 17 00:00:00 2001
From: f4exb <f4exb06@gmail.com>
Date: Fri, 5 May 2017 09:29:50 +0200
Subject: [PATCH] Added kernel >= 4.4.52 workaround for low latency serial
 devices (SerialDV)

---
 Readme.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Readme.md b/Readme.md
index 91303b533..97798165e 100644
--- a/Readme.md
+++ b/Readme.md
@@ -177,6 +177,12 @@ Although such serial devices work with a serial interface at 400 kb in practice
 
 Note that this is not supported in Windows because of trouble with COM port support (contributors welcome!).
 
+**Warning**
+
+Since kernel 4.4.52 the default for FTDI devices (that is in the ftdi_sio kernel module) is not to set it as low latency. This results in the ThumbDV dongle not working anymore because its response is too slow to sustain the normal AMBE packets flow. The solution is to force low latency by changing the variable for your device (ex: /dev/ttyUSB0) as follows:
+
+`echo 1 | sudo tee /sys/bus/usb-serial/devices/ttyUSB0/latency_timer`
+
 Alternatively you can use [mbelib](https://github.com/szechyjs/mbelib) but mbelib comes with some copyright issues (see next). If you have mbelib installed in a custom location, say `/opt/install/mbelib` you will need to add these defines to the cmake command: `-DLIBMBE_INCLUDE_DIR=/opt/install/mbelib/include -DLIBMBE_LIBRARY=/opt/install/mbelib/lib/libmbe.so`
 
 Possible copyright issues apart (see next) the audio quality with the DVSI AMBE chip is much better.