GNU ARM Eclipse: how to simulate pin input? - c

Question

I want to pass sine wave data onto a pin (any possible one), so that my program would be able to read it when being run in an emulator.
How how can I pass data in the form of (time:value) or just pass a function float generatorForPinX(int time); to act as signal generator into the GNU ARM Eclipse (I use QEMU but if any other emulator is required I am willing to migrate) board emulator?

Answer 1

These instructions are for emulating an Olimex STM32 P103 Development Kit.
Download and build
First download and build Qemu STM32, which includes patches for emulating the ADC peripheral on the STM32:
wget https://github.com/beckus/qemu_stm32/archive/stm32.tar.gz
tar xf stm32.tar.gz
cd qemu_stm32-stm32
./configure --target-list="arm-softmmu"
make
cd ..
If the configure step fails, then install the missing requirements. See the README for more information.
Then download the Olimex STM32 P103 Development Kit Demos:
wget https://github.com/beckus/stm32_p103_demos/archive/master.tar.gz
tar xf master.tar.gz
Look in stm32_p103_demos-master/demos/adc_single/main.c for an example program which uses the ADC.
Run the demo application
To build and run the adc_single demo:
cd stm32_p103_demos-master
QEMU_ARM_DIR=../qemu_stm32-stm32/arm-softmmu/ make adc_single_QEMURUN_TEL
(from another terminal) telnet localhost 7777
UART2 is attached to the telnet server on port 7777, which you should see output from. See the README for more information on how to build and run the demo applications.
Looking at the source for the adc_single demo application, it has 3 different modes:
Mode 1 (the default) will read from the temperature sensor on ADC channel 16
Mode 2 will read the Vdd value from ADC channel 16
Mode 3 will read from ADC channel 8.
The modes can be selected by using a button, but since we are emulating the hardware with QEMU, the button is not available. I switched between the modes by changing the int mode = 1; value and recompiling the program.
ADC emulation
The method that QEMU uses to emulate each ADC channel is viewable in the stm32_adc_start_conv function in hw/arm/stm32_adc.c:
static void stm32_adc_start_conv(Stm32Adc *s)
{
uint64_t curr_time = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
int channel_number=stm32_ADC_get_channel_number(s,1);
// Write result of conversion
if(channel_number==16){
s->Vdda=rand()%(1200+1) + 2400; //Vdda belongs to the interval [2400 3600] mv
s->Vref=rand()%(s->Vdda-2400+1) + 2400; //Vref belongs to the interval [2400 Vdda] mv
s->ADC_DR= s->Vdda - s->Vref;
}
else if(channel_number==17){
s->ADC_DR= (s->Vref=rand()%(s->Vdda-2400+1) + 2400); //Vref [2400 Vdda] mv
}
else{
s->ADC_DR=((int)(1024.*(sin(2*M_PI*qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)/1e9)+1.))&0xfff);
}
s->ADC_SR&=~ADC_SR_EOC; // jmf : indicates ongoing conversion
// calls conv_complete when expires
timer_mod(s->conv_timer, curr_time + stm32_ADC_get_nbr_cycle_per_sample(s,channel_number));
}
As you can see, ADC channel 16 will emulate a random Vdd input, ADC channel 17 will emulate a random temperature input, and all other channels will follow a sine wave from 0 to 2048. Here is a graph of the ADC values returned from all 3 modes:
If you want to have an ADC channel use a different emulation pattern, you can modify stm32_adc_start_conv and rebuild QEMU following the steps above.