Silicon Laboratories inc. sell MCU named Busy Bee, I decided to give it a try by transforming one in desperate firefly.
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The hardware is only 5 components including cell and its holder.
1 1K smd resistor
1 small red led
1 EFM8BB10F8G-SOIC16 MCU
1 CR2032 battery holder
1 CR2032 button cell
The MCU is glued on the back of cell holder using hot glue. Resistor and LED are glued on back of MCU using cyanate glue. See picture in images galery.
Firefly died last night without getting any answer to its desperate calls. It lastest less than 16 days. 4 days less than expected. Maybe the 240mah capacity was over evaluated. It was a no brand cell from China without specifications. The 240mah was taken from a known brand.
signing off.
I was not done yet. I decided to create a PIC10F200 version of desperate firefly.
The PIC10F200 is the simplest MCU available. As for peripherals it only have an 8 bits timer and a watchdog timer. 256x12bits words of flash memory and 16 bytes of RAM. It run on an 4Mhz internal oscillator. PIC execute instructions in 4 clocks cycles, this means 1 million instructions par second at most because branch and call needs 8 clocks cycles. Although the Fsys frequency can't be reduce to save power, the MCU can be placed in a low power mode using <i>sleep</i> machine code instruction. When in sleep mode the MCU can be reset by the watchdog timer overrun. So in this version the strategy was to put the MCU in sleep mode and use the watchdog timer to reset it at regular interval, set the new status of the LED according to message bitstream stored in flash memory and then put the MCU back in sleep.
The MPLABX project is included in PIC10F200_version on the github repository
I prefer to code these little MCU in assembler.
Jacques
include "P10F200.INC"
; LED connected on GP2
constant LED=(1<<GP2)
; sos message bit counter
constant count=16 ; this is a variable at address 16.
code
org 0
; hardware init
movlw (1<<NOT_GPWU)|(1<<PSA)|4
OPTION
movlw ~LED
TRIS GPIO
btfss STATUS,NOT_TO ; if a power reset clear count
goto next_bit
clrf count
next_bit:
movfw count
call sos
xorlw 0
skpz
bcf GPIO,GP2
skpnz
bsf GPIO,GP2
incf count
movlw .28
xorwf count,W
skpnz
clrf count
sleep
sos: ; data message 0=LEDoff, 1=LEDon
addwf PCL,F
dt 1,0,1,0,1,0,1,1,1,0,1,1,1,0,1,1,1,0,1,0,1,0,1,0,0,0,0,0
end
The measured current drain is very similar to the EFM8BB10F8G version.
The EFM8 MCU family is based on CIP-51 core which is a modernized version of Intel MCS-51, the core of 8051 MCU. CIP-51 core run faster . Here a document comparing CIP-51 performance with MCS-51 . It accept an external clock up to 25Mhz and have an internal oscillator running at 24.5 Mhz and a low frequency one at 80Khz. The core can be run from the HFO or LFO and there is frequency divisor at the output of the LFO as well as one for system clock, such at the CPU can be run at a very low frequency. The instruction set is 100% compatible with 8051. The MCU used in this project have 8KB flash and 512 bytes RAM. This RAM is splitted in 2 parts as 256 bytes regular RAM and 256 bytes XRAM.
The peripherals set as nothing to surprise one used to work with MCU. It include ADC, UART, TIMERS, analog comparators and 1 PCA (Programmable Counter Array) . The PCA is used for signal capture,PWM and frequency generation. It is equiped with a 16 bit counter and 3 comparator channels.
Configurator
The configurator is a visual tool to setup peripherals configuration and pinout assigment through the crossbar. The crossbar take in charge the connections betwen peripherals and MCU I/O pins. This visual tool save on hand written code. When the tool is closed the configurator generate a set of files containing code for the basic MCU configuration.
I concluded the first log on an image of configurator perspective. Now we will use this tool for configuration of this project.
I found a way around this bug. By double-clicking the warning message the Properties window display correctly.
It is instructive to look at the 3 source code files. For this simple project there not much in it nevertheless we have saved a lot of reference manual reading. Now only thing left to do is add our code in the file desperateFirefly_main.c// bit pattern to generate SOS morse code: dit,dit,dit,dah,dah,dah,dit,dit,dit
code char sos[4]={0xab,0xbb,0xaa,0};
//-----------------------------------------------------------------------------
// main() Routine
// ----------------------------------------------------------------------------
int main (void)
{
unsigned char b,c;
// Call hardware initialization routine
enter_DefaultMode_from_RESET();
b=0;
while (1)
{
c=sos[b/8]&(1<<(7-b%8));
b++;
if (b==28) b=0;
if (c)
P1&=~(1<<3); // port 1 pin 3 latch low LED ON
else
P1|=(1<<3); // port 1 pin 3 latch high LED OFF
}
}
about the code
The SOS message is stored in
code char sos[4]={0xab,0xbb,0xaa,0};
note de compiler directive code , At first I had used const instead expecting that the compiler would...
Read more »First step was to download and install Simplicity Studio. It is a free download requiring only an account registration. It is based on Eclipse IDE and provide Keil C51 compiler also free.
In spite of its name it is not simple as Arduino IDE. It is a full features professionnal tool. At first launch a guided tour is offered.
Right of tool bar there is a serie of icons. These are perspective selector icon. To create a project:
After a few seconds the IDE fall in configurator perspective. It will be the subject of next log of this project.
Nice work, don't forget to submit it to the Coin Cell Challenge!