Dell Venue 7 3740: How to get serial interface

2021-12-06T19:21:35Z

After experimenting with Intel Edison board I decided to have a look at Dell Venue 7 3740 which is based on the same chip (but has higher frequency and bigger eMMC, including LTE modem, display, and audio). It can be found on the second hand market for something like 60€ + delivery (as of day of writing this blog post).

Before doing anything useful it would be nice to have an access to the only free serial port (the same as for Intel Edison it's called /dev/ttyMFD2 in the stock kernel). For this, let's open a back cover and look at the motherboard:

Our interest here is the 40-pin connector which has last 4 pins related to the UART, but it's good that we may find necessary signals in better, from soldering perspective, locations as depicted below:

The signals are +1.8v TTL, be aware to find an appropriate adapter. Luckily I have had one which is +1.8v by default and connected directly to it, so +1.8v signal is unconnected in my case, while being soldered just in case:

The stock image doesn't issue anything to UART. However, if you rooted the device as pretty well described in the Dell official documentation, you would be able to run something like

adb shell
dmesg > /dev/ttyMFD2

(Note that default UART settings are 9600,8,n,1)

Next step is to build U-Boot for it, stay tuned!

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Dell Venue 7 3740: How to get serial interface