RTS on SparkFun's 5V FTDI Basic

Without a trick to help poor Arduino to restart SparkFun's 5V FTDI Basic breakout board could be more useful to me. To get hardware flow control from the board I did primitive fix: I made a bridge between pin 2 and 3 of FTDI232RL and cut off pin 2 on the board (see picture). After this kind of the Stone Age surgery connector's pin labeled as DTR actually carries RTS signal from FTDI232RL.

One new trick for an old dog

Well... There is no much trick in the ten pin 0.05" (1.27mm) ARM JTAG/SWD connector, but it is definitely new for "an old dog" - LPC2103.
A few weeks ago I received several small 0.85 x 1.26" (23 x 32mm) LPC210x header boards from BatchPCB. OpenOCD version 0.3.1 with FTDI2232 based adapter does work with LPC2103 on the board via new tiny JTAG connector. However, the OpenOCD configuration file needs minor adjustment since the connector has no TRST pin. So the reset configuration should include srst_only to let the OpenOCD know that TRST is not available.

CMSIS 2.0 Alpha

New Alpha version of CMSIS except adding Cortex-M4 support has replaced implementation of single assembly instruction functions by making them inline and moving code to dedicated header files (core_cmFunc.h and core_cmInstr.h) in CoreSupport folder. Thanks ARM! Now I can utilize original CMSIS code in my projects instead of coping functions with modified names to an additional header file. Nevertheless, the definition of __INLINE for GCC compiler still does not enforce actual inlining of the code as I described in the previous post. Well. I hope it will be fixed in the final release.

Using CMSIS with GCC

My interest in ARM Cortex-M3 based micros recently turned into some practical exercises with STM32-H103, GCC and Cortex Microcontroller Software Interface Standard (CMSIS) library. CMSIS is a useful set of definitions of Cortex-M0/M3 core architecture registers, data structures and interfaces to access core resources of a Cortex-M0/M3 based microcontroller. However, if you use GCC with CMSIS (v1.2.0 or v1.3.0) the definition of __INLINE macro provided in core_cm3.h and core_cm0.h:

#define __INLINE inline

does not force the compiler to actually inline the body of a function defined with __INLINE attribute. To tell GCC to inline the define should be:

#define __INLINE __attribute__((always_inline)) inline

Furthermore, __get_xxx, __set_xxx, __LDREX, __STREX groups of a single assembly line functions implemented as a regular functions as oppose to inline functions. Change of these functions to inline style allowed two times improvement of the performance of certain fragments of my code.

My take on SST

My search of some sort of OS suitable for N1's on-board computer based on LPC2103 lead me to an article "Build a Super Simple Tasker" (SST). The article describes a "run-to-completion (RTC) prioritized, fully preemptive, deterministic real-time kernel". Although I like the simplicity of the idea I think that tight coupling between an event and its target task in SST implementation (see Listing 3) reduces flexibility of the kernel. The Observer pattern is commonly utilized by event propagation frameworks including frameworks designed by Mother Nature. Additionally, an Observer pattern based design would allow to create and destroy tasks during an application run time. With these thoughts in mind, I decided to put together my own implementation of the idea. Since the coding has been completed I am using this implementation in two unrelated projects and should confirm that RTC tasks fit pretty nicely into FSM oriented designs and single event queue implementation of the Observer pattern provides nice to have extra flexibility with minimal impact on performance.

Number one

Number one (N1) is a robot which actually runs on a mobile phone. N1 has two parts: body and brain. The body consists of slightly modified chassis of N0 and tiny ARM® based computer which acts as brain spinal cord (BSC). N1 brain, located on a mobile phone and implemented as a Java ME program, connects to its BSC through Bluetooth®. There are some further technical details and photos on the robot's home page as well as a video which shows N1 equipped with infrared distance sensor in action.

Shrinkning Sharp GP2D120

I needed to mount vertically Sharp GP2D120 on a micro servo. To reduce sensor's dimensions I decided to get rid of standard mounting holes and connector. Removing mounting holes is simple job while removing the connector involves cutting a part of sensor's PCB. After a bit of head scratching, I moved a resistor and replaced several wires routed on the PCB under connector. Finally, I drilled two tiny holes on the top part of the sensor's body for a wire which attaches the sensor to the servo.