HOW TO: Make your own USB cable for HK-T6A calibration

April 27th, 2012 44 comments

Hey!

About a month ago I managed to go ahead and buy my first quadcopter (split the cost with two of my colleagues 🙂 ) and all the required equipment. I will do another post on that because it is really interesting!

I played around with RC airplanes some 10 years ago. There are some things changed now. Controllers are different. You are able to buy a 6 channel radio for under 30 Euros! Wow… Anyway, so I bought this controller from Hobbyking, named HK-T6A. However, I missed the fact that I needed a USB cable as well. To cut the story short, I had everything I needed to fly the brand new quad, but the controller needed calibration. Since the USB calibration cable was out of stock it would take some time to arrive. The cheap cables in ebay were shipped from China so it would take an additional month to get it. We had a problem!

Looking around in the internet, my attention was drawn to a picture of the transmitter communication socket. It was indicating TX/RX so I thought “wait a minute… could this be just serial comms?”. And so it was 🙂

What you need…

The only device you need is a simple USB-to-Serial (TTL) converter. If you are into digital electronics you should have a couple of them in your desk drawer. My personal favorite is CP2102. Take a look at my older post which I talk about this device. They cost only a couple of dollars including delivery from ebay. Check it out. You will also need 4 simple wires.

CP2102 USB-to-serial ttl module

The HK-T6 transmitter with the CP2102 and 4 wires. That is all you need!

Now take look at the trainer port of the controller.

The 4-pin din connection port of HK-T6

Connect everything together, really simple:

GND<–>GND
5V<–>5V
TX<–>TX
RX<–>RX

This is my temporary setup. It works!

Make sure your controller is switched off though. Then connect the CP2102 on your USB port of your PC. It could take some short time until your PC first finds the appropriate drivers and power the controller. You should see a red light on your transmitter. That means it is receiving power from the USB of your PC.

If something is not working, try switching the TX with RX lines. I mix them up all the time!!! You are now ready to calibrate your controller. Choose the software of your choice. I prefer Digital Radio. It is much better that T6Config. Note that this will work with FlySky CT6B since it is essentially the same controller.

Let me know if you need any help.

Categories: electronics Tags: , ,

Double Fine Adventure almost at $2,000,000

February 18th, 2012 No comments

If you haven’t already heard, this game already collected $1.9+ as a kickstarter project. WOW!!! I am also backing the project and I really hope it turns out well.

Those guys really deserve it. I have such great memories playing their games as a kid. Go Tim go!

 

I am a backer!!!

Categories: general Tags: ,

Using TMP100 temperature sensor with your PIC – PR5

January 31st, 2012 No comments

In this post I will describe how you can connect the TMP100 temperature sensor from TI to your PIC as well as receive temperature data. The sensor I am using is a generous sample from TI. Compared to the DS18S20 that I used before, this sensor is much faster, it takes 40ms to take a measurement with 0.5 degrees accuracy. The communication protocol is I2C. It could be a bit difficult connect it to your circuit since it is using a SOT-23-6 package.

For this project, I will be using my PIC prototyping board which carries a 18F4520. But you can pretty much use the C18 code in this post, with any PIC having a hardware I2C module.

Package problems!

Because SOT-23-6 is so small the first thing I needed was to create an adapter to make TMP100 compatible with my breadboard. This was a perfect excuse for improving my CNC skills :). So I created an adapter in EAGLE, cut it out using the CNC and then solder the sensor and 6 pins. The sensor is now breadboard ready!

The TMP100 adapter

 Connection

The connection is really simple. Add two pull-up resistors to the SDA and SDL lines. I used 10kOhm. The datasheet also suggests an optional capacitor on the supply.

TMP100 pinout

 

TMP100 Schematic

As you can see from the schematic there are two pins called ADD1 and ADD0. Those pins determine the I2C address of the sensor. You can find more details in the datasheet. I connected those two lines to GND therefore the address of the sensor I am using is 0x90. That’s all on the hardware side.

TMP100 – Point Register

I2c is the language this sensor talks :). So we need to use your PICs I2C hardware capabilities. Initialize your communications using

OpenI2C(MASTER,SLEW_OFF);

This sensor has a Point Register (PR)which (guess what!) points to the address of the register you want  to read or write 🙂 Before doing anything else we should point PR to the temperature register. To do that we have to initiate an I2C communication, send the address of the sensor and tell that sensor whether we like to write or read from it. This is done using a single byte. You see, the address is 7-bits starting from the MSB and bit 0 indicates whether is read or write operation (0=Write 1=Read). Let’s do an example. Our sensor’s address is 0x90. We wish to read something from the sensor so the byte should be 0x91. If we wish to write something to the sensors it should be 0x90. That’s it.

Therefore to write to point PR to the temperature register we should issue the following

StartI2C();
WriteI2C(0x90); // Call the sensor with WRITE
WriteI2C(0x00); // Write Temp reg to point register;
StopI2C();

Notice the 0x00? That is the address of the temperature register. The sensor is now ready to give us some temperatures.

TMP100 – Read that temperature

To read the temperature off the sensor, we need to call it using its address and READ (what we said above, remember?) and the sensor will transmit two bytes of data back. We read that using the appropriate I2C commands shown below. We have to acknowledge the reception of the bytes to let TMP100 know that we are ready for the next byte. Temperature is read as follows

StartI2C();
WriteI2C(0x91);
first_byte = ReadI2C();
AckI2C();
second_byte = ReadI2C();
StopI2C();

The temperature is made out of two bytes. If you don’t care about getting any decimals you can just use the first byte. The 4 most significant bits of the second byte contain information on the decimal value of the temperature.

TMP100 – C18 Library

I made a really simple library for tmp100 in C18. Just include the tmp100.h file to your project and make sure you initiate the I2C (the OpenI2C() command shown in this post) before calling any functions.

 

OK that is pretty much. You should be able to get some measurements out of that little sensor. If you need further help take a look at the example below

#pragma config OSC = HSPLL
#pragma config WDT = OFF
#pragma config PWRT = ON
#pragma config LVP = OFF
#pragma config PBADEN = OFF
 
#include <p18cxxx.h>
#include <i2c.h>
#include <usart.h>
#include <delays.h>
#include <p18f4520.h>
#include <stdio.h>
#include "tmp100.h"
 
void main(void) {
 
    unsigned int raw_tmpr;
    char str_tmpr[8];
 
    OpenUSART(USART_TX_INT_OFF &
              USART_RX_INT_OFF &
              USART_ASYNCH_MODE &
              USART_EIGHT_BIT &
              USART_CONT_RX &
              USART_BRGH_HIGH,
              21);
 
    Delay10KTCYx(250);
 
    OpenI2C(MASTER,SLEW_OFF);   // Initialize I2C module
    tm_setconf(0x60);   // Set sensor to full sensitivity
 
    while(1)
    {
        Delay10KTCYx(500);
        raw_tmpr = tm_gettemp();    // Get 2 bytes of temperature
        tm_tostr(raw_tmpr,str_tmpr);    // Convert the temperature to text
        printf("Temperature is %s\r",str_tmpr); // And output through USART
    }
    return;
}

I connected the USART TX/RX line using my CP2102 and used the cutecom program on Ubuntu to read the output on my PC. The screenshot below shows the terminal

The terminal on Ubuntu

1-Wire (OneWire) C18 library

November 17th, 2011 6 comments

So yesterday I wanted to get some temperature measurements from a DS18S20 thermometer to my PIC prototyping board. This thermometer uses the 1-Wire communication protocol so I searched around to find a 1-Wire library for the C18 compiler I am using. Maybe I am wrong but I couldn’t find any. So I created one, hence this post.

I had a post about the 1-Wire protocol a while back so you can read that if you are not familiar with it. To implement this protocol we need to work with precision timing. Ideally this could be written in asm. However, for convenience reasons I wrote this in C. I don’t really mind the minor performance penalty 🙂

Just to be clear, this is a library for the 1-Wire protocol, not for any of the supported devices. The library contains 3 main functions:

  • 1-Wire Reset
  • 1-Wire Write
  • 1-Wire Read

Using these three operations we can have full communication with any 1-Wire device. Let me demonstrate first and then I will write about how you can use it in your project.

A brief demonstration

To demonstrate this operation, I connected a DS18S20 thermometer and connected the DQ line on my PIC’s Port C Pin 1. The procedure I will follow is:

  • Issue a Reset pulse and observe the Presence of the thermometer
  • Issue the Skip Rom command (0xCC)
  • Issue the Convert T command (0x44)
  • Wait for 1+ second
  • Issue a Reset pulse and observe the Presence of the thermometer
  • Issue the Skip Rom command (0xCC)
  • Issue the Read Scratchpad command (0xBE)
  • And read the next two bytes which represent the temperature

Lets see the C code I loaded on my board Read more…

Categories: electronics Tags: , ,

Path Optimizer for pcb-gcode

November 13th, 2011 8 comments

The last couple of days I used the CNC machine to create a PCB for a project I am working on. As the CNC was etching away the copper, I noticed that between paths (i.e. while the spindle was not cutting) there was a lot of unnecessary travel. This happened quite a few times during my 35 minute job. Because I am using slow feedrate, about 10in/min, that unnecessary travel must have added 2-3 minutes. So if you are here looking how to optimize gcode you are at the right place 🙂

So to solve this, we need some optimization. What a better thing to spend your afternoon than firing up python, calling a friend and colleague over your PC, and solve this problem. So me and Mike, decided to solve this the easiest and quickest way possible, just by using brute force method to combine the different paths together. The goal is of course to minimize the unnecessary travel of the spindle.

Since this is a python script, it is multi platform. I personally tested it on my Ubuntu and Windows XP.

Some results

Let me just show you a couple of screen shots of a job, run on a simulator. This is the PCB of my last project. First let’s see the screenshot before optimizing the code

Spindle path before optimization

The white line represents the travelling between two paths. As you can see there are a lot of those white lines! 🙂 Now let’s see the second screenshot which is the same PCB job, but this time with optimized gcode

The path after optimization

As you can see the white lines are reduced. Also notice the clock (below the STOP sign)  of the simulator. We just saved a few minutes!

The program

First of all we assume that you already installed python on your system. Download the optimizer script. There is no GUI yet (feel free to expand the code, use git) so we need to run it from command line. Just write

python cncopt.py your_file_here

The script will run and give you some stats on the performance of the optimization.

Screenshot from my terminal

As shown, in my PCB gcode, the optimized code reduced the travel time from 33 inches to 14. That is a decrease of about 60%. The optimized file will have the same filename with an additional .optimized at the end.

Please note that this was a one-afternoon project just for the fun of it. All comments and feedback are welcome. I hope you find it useful.

I would like to thank Mike as we developed this together.

You can find the project on GitHub https://github.com/demestav/PCB-GCode-Path-Optimizer

Categories: CNC Tags:

How to flatten the CNC table

November 3rd, 2011 No comments

Hey guys, recently we got a medium-low end CNC machine in the lab I am working. We got it mainly for prototyping PCBs of our projects. I am still in the process of fine-tuning the machine. The learning curve was (is!) pretty steep and makes it even worst if you have little time to spend working the machine.

Anyway, when I printed my first PCB using 15 mils for copper width, I noticed some inconsistencies on the final result. One factor of this problem is the fact that the cutting table is not flat in relation to the XY axis of the machine. In other words, the distance between the table and the spindle is not constant along the plane.

This could happen for many reasons, your table may not be flat, the machine may not be exactly horizontally fixed to place etc. After asking around the web, the good fellas at the CNCzone.com forum, suggested to flatten the table surface by milling into it. So what that means is that you pass the cutting tool up and down, cutting out a square area on your table. Since the cutting tool is always at the same depth, the square are should be completely flat with relation to your cutting tool. Genius isn’t?

A nice and flat square on the wooden table!

In order to do that, you need the appropriate g-code of course. I search around a bit and found a software for that, but for some reason (bugs?) it wasn’t working well for me. For that reason and also because I wanted to learn Java Applet programming in a day :), I created a simple tool to create that square area for you.

Head over to CNC Tools page to find my online tool for for a flattening the CNC table. The tool will load into your browser and after you input your data it will give you the g-code and the estimated time to finish the job. You can test the generated g-code on a CNC simulator.

Let me know if you have any questions, suggestions or bug to report.

Categories: CNC Tags:

Serial Interface Between PIC and PC – PR4

October 4th, 2011 2 comments

This one is really useful.

Most of the times you are developing a project, you will need some sort of monitoring or visual output to understand the status of your program. Sure some LEDs blinking are great but some times you need more. This is where the good old serial communication comes in. Through this communication you will be able to send information in the form of data or text, to and from your computer. You can use it as a debugging tool to monitor what is going on in your microcontroller during execution time. Or you can use this communication to send data to the PIC for processing and then receive the result back. I am sure you will appreciate the usefulness of this as soon as you implement it.

And all this happens by sending a sequence of zeros and ones… Read more…

Categories: electronics, projects Tags: , ,

PIC and 5110 Interface with SPI hardware – PR3

September 26th, 2011 11 comments

This is the first “official” project I am doing with my PIC prototyping board. This project is about interfacing and using a simple Graphic LCD. So to follow this project you need a PIC to have SPI hardware, in order to communicate with the device. The GLCD (Nokia 5110) I am using is well known in the community and it is a cheap device. I bought it off ebay for about 5 Euros. Read more…

Categories: electronics, projects Tags: , , , ,

PIC Prototyping Platform – PR2

September 7th, 2011 No comments

Hey,

In PR1 project, I talked about creating a stable prototyping platform that would save me from the trouble of setting up the microcontroller and all its required components. However, since then, I worked on tidying up this design into a more usable design (I wanted to play around with creating PCB actually 😀 ). So I designed the board sent it for fabrication and finally put it together. Read more…

Categories: electronics, projects Tags: , ,

Components for the Prototyping board arrived!

September 1st, 2011 3 comments

Hey guys,

A couple of days ago, the components for my new PCB arrived so I was able to test my design. The result was successful! Personally this was a simple board carries a lot of “firsts” for me. To begin with, it was the first time I ever designed a board on EAGLE that became an actual PCB. This might sound stupid but its different to make a design for home production (using chemicals) and a design that includes 2 layers, vias, solder masks, silkscreens, correct drill holes etc. I am not saying its hard, I am just saying its different so there are new things to consider.

Another “first” was the soldering of a TQFP package which as it turns out its not that hard (actually its like magic ;))! I had to buy some solder paste and a tweezers to make my life easier. I am suggesting to check out Surface Mount Soldering guide if you are interested.

Anyway, for a first attempt, I believe the results are pretty good. I made a simple blinking LED program which works, the power switch and reset button work, so I am assuming the design is OK.

I will make another post soon to include the schematics and stuff if anyone is interested and hopefully start producing some projects on this proto board. Finally here are a couple of pictures of the board:

Looking good!

Dimensions are 5cm x 5cm