On the TWR-LCD, I’m using a USB MSD bootloader. In Programming part of flash I showed how to download and debug the application on top of the bootloader. But how to debug both the bootloader and the application? At the same time with CodeWarrior for MCU? The magic key is tell CodeWarrior to use ‘Other Executables’.
There was one part missing to complete the software support for my Arduino DataLogger Shield on top of my FRDM-KL25Z Freedom board: support for the Maxim DS1307 RTC (Real Time Clock).
DS1307 on the Adafruit Data Logger Shield (Source: http://www.ladyada.net/make/logshield/design.html)
Things got delayed a bit, as I first needed to get the I2C infrastructure up and running (see this post). But finally, I have things working :-). I proudly present: RTC_Maxim!
I really hate this kind of stuff: I know it should work, but it does not. I’m loosing a lot of time (hours, days, even weeks) to track it down to the root cause. Yes, I create my own bugs. Yes, there are bugs in tools, sources, libraries and components. But what many might not believe: there are bugs in silicon too :-(. If you do not believe, here is one: there is a hardware I2C problem on the KL25Z used on the Freedom board. It worked in one project, but not in another.
❗ The silicon bug described here is present on many Kinetis devices, not only the KL25Z!
Logic Analyzer attached to the FRDM-KL25Z board
So if you are facing a problem where you read 0xFF or wrong values from the I2C bus with the KL25Z, here is probably why (and how to workaround it). The problem showed up with a modified version of the Freedom Accelerometer tutorial….
I’m working with the I2C bus recently a lot. I’m using it in a project to reverse-engineering skimming (credit card fraud) devices. I needed to improve one of my applications for the lecture classes where a MCF52259 is communicating with a TWR-LCD display over I2C. And I want to add RTC (Real-Time-Clock) capabilities to my Arduino Data Logger Shield which requires I2C.
The same time I want to have things working with ARM Cortex-M4 and M0+ devices. And here the challenge started: using the I2C_LDD (Logical Device Driver) Processor Expert components for the ARM Kinetis devices is definitely not simple and easy. I want to use my software compatible for both the ARM cores and say for S08 and ColdFire cores. So what I ended up is to write a ‘generic’ I2C driver on top of the low level Processor Expert components: named GenericI2C.
Generic I2C Component
“Anything that can go wrong, will go wrong”.
strikes again. Well, the modified version of it:
“Anything that can go wrong, will go wrong, but it will wait until it really, really goes wrong”.
It is always amazing to see that systems having a fundamental flaw, they can work for a long period. Only that on day X my application crashes. And when found the problem, I’m wondering how in the world it was *ever* working with that bug in it :-(.
It is as bad as this: my application stopped in an unhandled interrupt service routine:
That does not tell much. I’m using Processor Expert generated code, and with this all my ‘unhandled’ vectors are pointing the same handler:
Continue readingOne success factor of the Arduino platform is the broad availability so-called ‘shields’: hardware plugin-modules which extend the capability of platform. Shieldlist.org currently lists 288 different shields available! Clearly, Freescale wants to benefit from that ecosystem with the Freedom FRDM-KL25Z board which features Arduino compatible headers. Time to use the Freedom board with an Arduino shield :-).
Data Logger Shield on Top of Freedom Board
In “A Shell for the Freedom KL25Z Board” I have presented an application which implements FreeRTOS, LED’s and a shell using the UART on the KL25Z over OpenSDA. So why not adding native USB CDC to the mix? Using both the USB and CDC with the same shell?
So what I have added is that the shell runs on both the SCI (over OpenSDA) and USB CDC (with the KL25Z). For this, the FSL USB CDC software stack is now part of the project:
Shell Project with USB CDC
Sometimes it is necessary to write an interrupt service routine in assembly language. This is the case as well for the ARM Cortex-M0+ which is found in the KL25Z on my Freedom board. But there is something important about the ARM Cortex architecture: Thumb Mode.
Thumb mode the ‘ARM way’ to reduce the code size with a reduced (16bit wide) instruction set. The ARM architecture can implement a ‘mixed’ mode, on a function level. To distinguish between ‘normal’ ARM functions and ‘thumb’ functions, the processor is checking if the LSB (Least Significant Bit) of a function pointer (or function call destination) is set. So a jump address of 0x410 is for a ‘normal’ function, while a function jump to the address 0x411 (even if the function is located at the address 0x410) denotes a ‘thumb’ function.
Checking the download statistics of my Processor Expert components on http://www.steinerberg.com/EmbeddedComponents/, there is a clear winner: FSL_USB_Stack 🙂
It has been a while I presented that universal USB CDC component in this blog. The component has received a larger re-architecture, I wanted to support more than just USB CDC. For this, the CDC part is now present in a separate sub-component:
FSL_USB_Stack with Sub-Components
MCU on Eclipse 