• RS232 DB9 Pinout

    11/16/2020 at 08:52 0 comments

    It seems I always struggle with RS232 DB9 pinout. This page is to track it.

    A good reference for DB9 can be found in FTDI RS232 Cable. See Datasheet page 17.

    The RS232 connector (Male) has the following pinout, i.e configured as a Data Terminal Equipment (DTE).

    Male DB9 RS232
    Male DB9 RS232
    1InputDCD = Data Carrier Detect
    2InputRXD = Receive Data
    3OutputTXD = Transmit Data
    4OutputDTR = Data Terminal Ready 
    5GroundGND = RS232 signal ground
    6InputDSR = Data Set Ready
    7OutputRTS = Request To Send 
    8InputCTS = Clear To Send
    9Input / PowerRI = Ring Indicator

    The device this adapter connects to should follow the following pinout.

    The RS232 device connector is then female, configured as Data Communication Equipment (DCE).

    Female DB9 RS232
    Female DB9 RS232
    1OutputDCD = Data Carrier Detect
    2OutputRXD = Receive Data
    Aka Device Transmit pin (DT-in/DC-out)
    3InputTXD = Transmit Data
    Aka Device Receive pin (DT-out/DC-in)
    4InputDTR = Data Terminal Ready 
    5GroundGND = RS232 signal ground
    6OutputDSR = Data Set Ready
    7InputRTS = Request To Send
    8OutputCTS = Clear To Send
    9Input / PowerRI = Ring Indicator

    The data flow in summarized as follow.

    DTC to DCE
    DTC to DCE

  • Dell Precision 3541 Review

    09/29/2019 at 02:10 0 comments

    I selected the Precision 3541 with the following configuration :

    • Intel i5-9400H
    • Intel GPU
    • 97Wh battery

    I upgraded to the following memory and SSD :

    One thing I was looking for was to be able to play 4K UHD HDR movies. I assume the on-board HDMI 2.0 would be able to support it. I should have done my research before as HDR is only supported on HDMI 2.0a.

    The Type-C port allows a lot of versatility. Using a Type-C to HDMI 2.0b adapter, I am able to play 4K UHD HDR 10bit @ 30Hz. The color space is reduced if the refresh rate is increased to 60Hz. See UPTab USB C to HDMI 2.0b Active HDR Adapter 4K 60Hz.


    The i5-9400H is integrated with a 35W profile as listed in Intel TDP-down configuration. I was interested to find how this TDP-down was performed.

    By default the Turbo Boost Max Power is set to 35W. This limit can be changed with Intel Extreme Tuning Utility (XTU). 

    Summary :

    • Cinebench R20 @ 35W : 1758pts
      • Temp 86°C
      • Freq 3.30 GHz
    • Cinebench R20 @ 45W : 1892pts
      • Temp 94°C
      • Freq 3.63 GHz
    35W TDP
    45W TDP

    Increasing the TDP to 45W needs to be done manually. How it is reset to 35W is unknown. The configuration shown by Intel XTU shows 45W Turbo Boost Max Power but the system runs at 35W.

    Note on the cooling solution :

    • On Intel GPU system, there is only 1 heat pipe from the CPU to the fan assembly
    • The fan speed let the system heat up before ramping up. The balance between fan noise and heat is always a challenge.
    • Rising the laptop from the table leads to better temp : 78°C after Cinebench @ 35W

    Intel XTU shows the different CPU settings for the i5-9400H

  • Zotac EI751 Repasting

    12/09/2018 at 00:49 0 comments

    I got my EI751 at the beginning of 2016. After 2.5 years it was becoming a bit loud and hot.

    I got around to repasting it mid 2018, this is the log.

    I removed the screws holding the board down. This voids the warranty which is not ideal. It was quite tricky to pull the board out. I ended bending the enclosure where the antenna connector is. The top cover is actually screwed to the main shell, don't try forcing anything.

    The fan comes off with a bit of force as thermal pad sticks to the heatsink and the board. Have some thermal pad to replace the old one, 1.5mm tick should do it. The heatsink cover the CPU and the PCH.

    Testing with Intel XTU indicates thermal throttling and current limit throttling. Eventually a better cooling solution could be fitted ( would not use the standard case ). Then the actual power delivery may be the limiting factor. I may try to improve the cooling and build a custom case after I renew this computer.

    Prim95 load leads to thermal throttling and power limit throttling. With a better colling and increasing power limits, the boost clocks could be maintained.

    I wish there was more SATA slot as the single driver will not make the best media center. Improve cooling would go a long way to make this PC more silent to go by a TV.

    Intel I7 5775R - Intel XTU Tuning Control.