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xp 3a

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BLHeli Flashing Setup

There were some confusion on what’s the minimum things to plug in to properly flash BLHeli onto the the ESC. I know I had the same questions when I started out and when you run into a problem, there are too many variables to contend with.

An overhead view of how I have mine set up. You don’t need anything more than this to properly flash the ESC.

The minimum setup to allow BLHeli flashing.

And for completeness, here is the order of how I hook things up.

  1. First, I connect the ESC to the USB Toolstick.
  2. Next, I connect the USB Toolstick to the computer.
  3. Finally I connect the battery to the ESC to power it up.

I then open up the BLHeliSuite program that user 4712 from HeliFreak wrote.

I click on the “Flash BlHeli Hex File” button. Then select the proper firmware I want to flash over and hit the “OK” button to flash the new firmware onto the ESC. (You’ll get prompted with a couple of dialog boxes warning that you’re about to overwrite the original firmware on the ESC. I just answer ok to dismiss them and continue on.)

Let me know if that helps you or if I need to clarify any steps.

Categories: Brushless
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Silicon Labs USB Toolstick Mod for BLHeli Flashing

This is part 1 of my series on the Blade mSR X Brushless Conversion using Steffen’s BLHeli firmware for the XP 3A ESC. The information in this post is also applicable for those of you doing a brushless conversion on the Blade mCP X and will be flashing the XP 7A and XP 12A ESC. All those ESC, along with the DP 3A and Supermicro 3.5A uses a Silicon Labs based chip, so you will need to do the following modification.

Step 1: Obtain the SiLabs USB Toolstick:

The USB Toolstick can be purchased from Digi-Key or from Silicon Labs themselves. Digi-Key ships it out fast and there was no order minimum.

Step 2: Open the USB Toolstick:

Using a guitar pick or a folded over piece of plastic from toys/food packaging, you can insert between the halves like so and twist to pop the halves apart. Then work around the perimeter to easily open the plastic case to get into PCB board. This prevents any damage to the plastic housing which we will reuse later to reassemble the USB Toolstick.

Wedge a piece of plastic to open up the USB Toolstick

Step 3: Soldering Points – Wiring:

Here’s the solder points you need to be aware of. We will use red, black and white wires to match Steffen’s original post.

  • Side A: Here is where to solder the white (C2Data) wire. It also shows the two pins (2 and 4) that will need to be soldered together. (Alternatively, if you need to be able to use the USB Toolstick for other projects, you can simply wire up a switch that when enabled, bridges those two pins.)

The white wire solder point and the two pins you need to solder together.

  • Side B: On the reverse side, you can solder a red (C2CLOCK) and black (GND) wires to these two legs.

Solder the red and black wires to these pins.

I run the red and black wires through the holes so all three wires are on one side like so.

SiLabs USB ToolStick all wired up.


Step 4: Drill holes for the connector:

I wanted to add a connector. So I drilled 3 holes into the USB ToolStick’s case. This was easily accomplish by temporarily taping the connector I am using to the case to act as a template. Then used a 1mm drill bit to drill at each point of the connector legs. Simply insert the connector through the Toolstick housing and soldered up the red, black and white wires to it. The connector should be held in tightly if done right. The connector I used came with my XP 3A ESC.

Alternatively, you can simply drill a single hole to pass all three wires through the case. Then solder up a connector to them outside the case.

Here is a photo of the result of this step. I can see the position for the black, red and white wires to help me orient the mating plug that goes to the ESC.

USB ToolStick with connector


Step 5 Final: Reassemble USB ToolStick Case:

Once the wiring is done, it’s easy to snap back on the case you took apart in step 1. Here is a look at the modified USB ToolStick with the connector installed into the case. We are ready to use the modified SiLabs USB Toolstick to flash the ESC with BLHeli firmware. This will be outlined in Part 2 of the mSR X Brushless Conversion series.

SiLabs USB ToolStick modified for BLHeli Flashing.


Categories: Brushless
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Hobby King’s XP 3A Brushless ESC

For those looking to upgrade the MOSFET on the XP 3A, here are the location of the N-Fets and P-Fets.

Location of the N channel and P channel MOSFET on the XP_3A

You can replace the N-FET with the DMN2041. This takes the resistance of the original FETs from approximately 30 mOhms down to 26 mOhms or even 13 mOhm stacked as mentioned below.

The P-FET can be replaced with the DMP2035. The P-FETs original resistance is approximately 60 mOhm. Replaced with the better quality FETs, you take it down to ~30 mOhm or 15 mOhm stacked. Quite a difference. Less resistance means less heat and more power going to the motors.

As alluded to above,  stacking two or three of them together effectively lowers the resistance and basically “upgrade” the ESC so it can handle more current through them. Here’s a great tutorial from AtomicMods that demonstrate how to stack FETs.

Tutorial 1:28 XMODS Generation 1 Stacked FET Installation

See this awesome thread and work by Steffen, author of BLHeli brushless ESC firmware code where I gleamed much of this information. Look for more post on the subject as I attempt to convert a mSR X and Xieda 9958 to utilize a brushless motor.

Categories: Brushless, Helicopter
2 Comments on Hobby King’s XP 3A Brushless ESC