I admit: I have used ARM Cortex cores a lot in the recent months. Yes, I think with the ‘ARM domination of the world’ over time the ARM core will blast away probably all other cores, except for niche players? Still, there are reasons to use non-ARM cores, and even if it is just that I have a board at hand :-).

Flexis?

So I do have two Freeescale DEMOQE boards which I have not touched much in the last two years. Freescale introduced these boards with the ‘Flexis’ cores: a nice concept to ease the migration from 8bit (Freescale S08 core) to the 32bit world (Freescale ColdFire core). The DEMOQE (and DEMOJM) boards came with red 32bit and green 8 bit processor modules. The processors in each family are pin compatible, so it is very easy to change from 8bit to 32bit and back. I loved that concept, as with the same peripherals, it was possible to explore the power of a 32bit core. With the move of Freescale into the ARM domain, things got calm on this domain, and I feel that this great concept has been abandoned by Freescale? Why not having the same concept say from 8bit S08 to ARM, or 32bit ColdFire to 32bit ARM? That would be awesome! Yes, that Big Endian to Little Endian would be a challenge. But I would *love* to have the S08 peripherals on an ARM core! The S08 (and S12) peripherals are so much better what Freescale has on the ARM Kinetis parts, and I’m not alone with this opinion. I started to truly value the S08 peripherals once I move to the Kinetis parts: it is like day and night from the functionality, stability and easy-to-use aspects. Yup, I stop whining now, as I know the future is ARM and 32bit, but I hope that the goodies of the 8bit world will migrate to the ARM world.

RNet on 8bit?

I’m a believer that software and stacks are only good if they run on multiple platforms and cores. I have developed the RNet wireless stack and use it mainly on ARM Cortex M0+ (see this post). Having a stack running with different transceivers, compilers and microcontroller for sure helps to improve it. So for this article I run the RNet stack with the Freescale MC13201 transceiver card. In case you want to run the stack on a different microcontroller, the porting details in this post should help you.

The example project discussed in this article is available on GitHub.

DEMOQE Connections to Transceiver

The DEMOQE board has a connector on the downside of the board making it easy to extend it to a custom board. I have created a breakout board for the MC13201, so I have wired the two boards together:

The pin connections are as below:

=================================================================
THIS FILE WAS GENERATED BY "Processor Expert version 10.3 for Freescale Microcontrollers".
Project "ProcessorExpert", 2013-12-25, 10:51, # CodeGen: 26
DO NOT MODIFY IT.
=================================================================

=================================================================
 SIGNAL LIST
-----------------------------------------------------------------
SIGNAL-NAME [DIR]        => PIN-NAME [PIN-NUMBER]
-----------------------------------------------------------------
LED0 [Output]            => PTC0_TPM3CH0 [34]
LED2 [Output]            => PTC1_TPM3CH1 [33]
LED3 [Output]            => PTC2_TPM3CH2 [25]
LED4 [Output]            => PTC3_TPM3CH3 [24]
LED5 [Output]            => PTC4_TPM3CH4_RSTO [78]
LED6 [Output]            => PTC5_TPM3CH5_ACMP2O [77]
LED7 [Output]            => PTE6 [20]
LED8 [Output]            => PTE7_TPM3CLK [7]
Radio_ATTN [Output]      => PTG1 [73]
Radio_CE [Output]        => PTD1_KBI2P1_MOSI2 [1]
Radio_CLK [Output]       => PTB2_KBI1P6_SPSCK1_ADP6 [40]
Radio_IRQ [Input]        => PTD0_KBI2P0_SPSCK2 [2]
Radio_MISO [Input]       => PTB4_TPM2CH1_MISO1 [23]
Radio_MOSI [Output]      => PTB3_KBI1P7_MOSI1_ADP7 [39]
Radio_RESET [Output]     => PTH0 [19]
Radio_RTXEN [Output]     => PTH1 [18]
RxD [Input]              => PTB0_KBI1P4_RxD1_ADP4 [42]
TxD [Output]             => PTB1_KBI1P5_TxD1_ADP5 [41]
=================================================================

=================================================================
 PIN LIST
-----------------------------------------------------------------
PIN-NAME [PIN-NUM]       => SIGNAL-NAME [DIRECTION]
-----------------------------------------------------------------
PTB0_KBI1P4_RxD1_ADP4 [42] => RxD [Input]
PTB1_KBI1P5_TxD1_ADP5 [41] => TxD [Output]
PTB2_KBI1P6_SPSCK1_ADP6 [40] => Radio_CLK [Output]
PTB3_KBI1P7_MOSI1_ADP7 [39] => Radio_MOSI [Output]
PTB4_TPM2CH1_MISO1 [23]  => Radio_MISO [Input]
PTC0_TPM3CH0 [34]        => LED0 [Output]
PTC1_TPM3CH1 [33]        => LED2 [Output]
PTC2_TPM3CH2 [25]        => LED3 [Output]
PTC3_TPM3CH3 [24]        => LED4 [Output]
PTC4_TPM3CH4_RSTO [78]   => LED5 [Output]
PTC5_TPM3CH5_ACMP2O [77] => LED6 [Output]
PTD0_KBI2P0_SPSCK2 [2]   => Radio_IRQ [Input]
PTD1_KBI2P1_MOSI2 [1]    => Radio_CE [Output]
PTE6 [20]                => LED7 [Output]
PTE7_TPM3CLK [7]         => LED8 [Output]
PTG1 [73]                => Radio_ATTN [Output]
PTH0 [19]                => Radio_RESET [Output]
PTH1 [18]                => Radio_RTXEN [Output]
=================================================================

For the transceiver connection, the following signals are required:

1. SPI connection with CE, MISO and MOSI
2. Radio ATTN, RXTXEN and IRQ

SPI Settings

The SPI communication is implemented with the SynchroMaster component:

The SPI needs isconfigured as below:

• No interrupts (the low-level driver for the MC13201 is not using interrupts (yet)).
• MISO, MOSI and Clock pin. No slave select pin, as handled in the tranceiver driver.
• Clock edge: falling (data on the SPI is shifted on the falling edge)
• Most Significant Bit (MSB) first
• Clock idle polarity: Low
• SPI clock settings: list of values (details below)

SPI Clock Settings

The SPI bus can be used by other components too (although I admit I have used the MC13201 as the only device on the bus). Anyway, to support multiple bus participants, the bus needs to be set up with a ‘list of values’. For this I click on the ‘…’ for the clock settings (you need first to click into the field!):

The MC13201 can run up to 8 MHz SPI clock. So I configure it to use a list of values, and use a value <= 8 MHz for the Mode (index) zero:

I will use that index zero later in the transceiver settings.

Transceiver Settings

The pins for the transceiver are configured inside the SMAC component:

Transceiver Properties

In the transceiver settings I configure the transceiver type, point to the SPI ‘list of values’ index zero (see SPI settings above):

IRQ Settings

The interrupt pin is configured with pull-up and to generate an interrupt on falling edge:

What is left over is the probably most complicated part: the configuration of the IRQ (interrupt) pin of the transceiver. Processor Expert usually makes things easy, but in the case of interrupt pin handling important functionality is missing in the interrupt API: there is no way to acknowledge the interrupt pin from the driver :-(. Instead, I need to define a macro to acknowledge the interrupt so I can use it in the driver.

First I need to know how to clear the flag. This I can get from the Processor Expert code generated for the IRQ pin I have assigned:

This code I can use in my settings. I click the ‘…’ for the string list:

Then I assign the code to the IRQACK() macro:

CPU Settings

As the stack transceiver can use low power wait mode, I enable that method in the CPU component:

RNet Integration

The RNet integration is very similar for the ARM Cortex (see this post and this post). For the MC13201 transceiver I need to link the interrupt event to the event handler in the Radio.c module. For this I add an include to Events.c:

/*
** ===================================================================
**     Event       :  SMAC1_OnInterrupt (module Events)
**
**     Component   :  TRSVR1 [MC13192]
**     Description :
**         Event raised in case of transceiver interrupt.
**     Parameters  : None
**     Returns     : Nothing
** ===================================================================
*/
void SMAC1_OnInterrupt(void)
{
  RADIO_OnInterrupt();
}

Not to forget to include the header file at the top of Events.c:
#include "Cpu.h"
#include "Events.h"

/* User includes (#include below this line is not maintained by Processor Expert) */
#include "RadioSMAC.h"

That’s it 🙂
Shell Interface
The demo features a simple console/shell interface:
RNet with DEMOQE
Trouble Shooting
What follows is more about dealing with known issues in Processor Expert and CodeWarrior for 10.5 😦
Processor Expert, S08 and RTOS in MCU10.5
Processor Expert fails to add the correct RTOS initialization code for S08 targets. To fix this, add the following code to main():
void main(void)
{
/* Write your local variable definition here */
#ifdef PEX_RTOS_INIT
PEX_RTOS_INIT();                   /* Initialization of the selected RTOS. Macro is defined by the RTOS component. */
#endif

Banked Memory Model for S08 in MCU10.5
It looks like debugging for banked memory model is broken in MCU10.5 :-(. I thought I saw a patch for this somewhere on the Freescale web site, but I have found it. So my project on GitHub is using the small memory model. I was able to use banked memory model with MCU10.3.
Do NOT load projects with different Eclipse versions!
The other thing is: do NOT try to load the same project with different Eclipse versions! It is ok to load say a 10.4 project into 10.5 (upwards compatibility). But once you loaded it in a higher version, bad things can happen if you load it with an earlier version (e.g. 10.4), and then again in a newer version (10.5):
CW ProjectsView Project Loading Verification Error
This problem is reported in the Freescale Forum too.
❗ This is a nasty thing, but common to many tool chains, not only Eclipse (I had similar things with IAR too). As a general advise: never load ‘never’ projects with ‘older’ IDE versions. It might work sometimes, but if things can go bad, they will.
Summary
Although things are moving to 32bit ARM cores, using software and stacks with 8bit cores still can make sense, especially if they are at hand ;-). Apart of that, using the stack with the 8bit HCS08 allowed me to fix some minor issues, and if it is only to fix possible compiler warnings for my source code. The full project and sources are available on GitHub.
Happy 8biting 🙂

		
	
			

			
			
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