The objective of an alcohol detector is to accurately and reliably measure the presence of alcohol in a person's breath, blood, or other bodily fluids to promote safety and responsible behavior. This device aims to:
- Prevent Impaired Driving
- Ensure Workplace Safety
- Enhance Public Health
The Breath Analyser consists of the MQ3 sensor. Paired with the RISC-V processor. MQ3 sensor module has a built in LM393 precision comparator which converts the anlog signal to digital output for the RISC-V. The module includes a potentiometer for adjusting the sensitivity of the digital output (D0). You can use it to set a threshold so that when the alcohol concentration exceeds the threshold value, the module outputs LOW otherwise HIGH.
Rotating the knob clockwise increases sensitivity and counterclockwise decreases it.
Setting the threshold
The module has a built-in potentiometer for setting an alcohol concentration threshold above which the module outputs LOW and the status LED lights up.
Now, to set the threshold, let the alcohol vapors enter the sensor and turn the pot clockwise until the Status LED is on. Then, turn the pot back counterclockwise just until the LED goes off.
That’s all there is to it; your module is now ready to use.
The block diagram of the breath analyser is given below.
// Function to analyse whether the given person is drunk or not
//#include<stdio.h>
int main() {
int sensor_status;
int buzzer;
int masking;
int i;
int sensor_state;
int Alcohol0,Alcohol1;
//for (int j=0; j<15;j++) {
while(1){
/*
if(j<10)
sensor_status=1;
else
sensor_status=0;
*/
asm volatile(
"or x30, x30, %1\n\t"
"andi %0, x30, 0x01\n\t"
: "=r" (sensor_state)
: "r" (sensor_status)
: "x30"
);
if (sensor_status == 0) {
// If alcohol is below the permissable limit, set the buzzer control register to 0 (buzzer off)
masking=0xFFFFFFFD;
// printf("No alohol detected \n");
buzzer = 0;
asm volatile(
"and x30,x30, %0\n\t" // Load immediate 1 into x30
"ori x30, x30,2" // output at 2nd bit , keeps buzzer in off
:
:"r"(masking)
:"x30"
);
asm volatile(
"addi %0, x30, 2\n\t"
:"=r"(Alcohol0)
:
:"x30"
);
//printf("Alcohol0 = %d\n",Alcohol0);
}
else {
// If Alcohol is above the permissible limit, set the buzzer control register to 1 (buzzer on)
masking=0xFFFFFFFD;
buzzer = 1;
// printf("Alcohol presence detected \n ");
asm volatile(
"and x30,x30, %0\n\t" // Load immediate 1 into x30
"ori x30, x30,2" //// output at 2nd bit , switches on the buzzer
:
:"r"(masking)
:"x30"
);
asm volatile(
"addi %0, x30, 0\n\t"
:"=r"(Alcohol1)
:
:"x30"
);
//printf("Alcohol1 = %d\n",Alcohol1);
}
// printf("buzzer=%d \n", buzzer);
}
return 0;
}
riscv64-unknown-elf-gcc -march=rv32i -mabi=ilp32 -ffreestanding -nostdlib -o ./out Alcohol.c
riscv64-unknown-elf-objdump -d -r out > Alcohol_Detector_assembly.txt
out: file format elf32-littleriscv
Disassembly of section .text:
00010054 <main>:
10054: fd010113 addi sp,sp,-48
10058: 02812623 sw s0,44(sp)
1005c: 03010413 addi s0,sp,48
10060: fec42783 lw a5,-20(s0)
10064: 00ff6f33 or t5,t5,a5
10068: 001f7793 andi a5,t5,1
1006c: fef42423 sw a5,-24(s0)
10070: fec42783 lw a5,-20(s0)
10074: 02079463 bnez a5,1009c <main+0x48>
10078: ffd00793 li a5,-3
1007c: fef42223 sw a5,-28(s0)
10080: fe042023 sw zero,-32(s0)
10084: fe442783 lw a5,-28(s0)
10088: 00ff7f33 and t5,t5,a5
1008c: 002f6f13 ori t5,t5,2
10090: 000f0793 mv a5,t5
10094: fcf42e23 sw a5,-36(s0)
10098: fc9ff06f j 10060 <main+0xc>
1009c: ffd00793 li a5,-3
100a0: fef42223 sw a5,-28(s0)
100a4: 00100793 li a5,1
100a8: fef42023 sw a5,-32(s0)
100ac: fe442783 lw a5,-28(s0)
100b0: 00ff7f33 and t5,t5,a5
100b4: 000f6f13 ori t5,t5,0
100b8: 000f0793 mv a5,t5
100bc: fcf42c23 sw a5,-40(s0)
100c0: fa1ff06f j 10060 <main+0xc>
Number of different instructions: 11
List of unique instructions:
sw
andi
li
addi
and
j
mv
or
bnez
ori
The output of the spike is shown below where sensor value =1, indicates Presence of Alcohol is detected and buzzer is turned on i.e buzzer =1, contrary to that if presence of alcohol is not detect buzzer is off, the image shows output as 2 whose binary equivalent is 10.
The below image shows the change in output with respect to change in input. Low value of input indicates that the alcohol consumption is under permissable limmit and buzzer is off i.e output is also low, contrary to that when the person has drunk above permissible limit output of the sensor which is input to the processor is high and buzzer is turned on.
Toggle in input is reflected in output as well.
The below image shows clock of the system, top gpio pins, Instruction ID.
The below image shows increament in Instruction ID, which implies that execution of instructions from the program counter.
The below image shows that with change in the instruction ID, when input changes output value is changed corresponding to that.
The below image having two markers marked showing the delay for output change with respect to change in input.
| Input value with time stamp | Output Value with time stamp | Delay |
|---|---|---|
| 1(4500Sec) | 1(4530Sec) | 30 Sec |
| 0(5000Sec) | 0(5050Sec) | 50Sec |
The input toggling is given for 500units in the testbench code, the same is reflected in the waveform.
The below image shows that input value is read at the instruction and corresponding value dumping in the output.
| Input Instruction ID & Value | Output Instruction ID & Value |
|---|---|
| 1 (FEF42423) | 1(02079463) |
To perform the gate level simulation following commands were used
read_liberty -lib sky130_fd_sc_hd__tt_025C_1v80_256.lib
read_verilog processor.v
synth -top wrapper
dfflibmap -liberty sky130_fd_sc_hd__tt_025C_1v80_256.lib
abc -liberty sky130_fd_sc_hd__tt_025C_1v80_256.lib
write_verilog Synth_test.v
To run the GLS command following commands were used
iverilog -o test synth_processor_test.v testbench.v sky130_sram_1kbyte_1rw1r_32x256_8.v sky130_fd_sc_hd.v primitives.v
The same results i.e. output following input is replicated in the Gate level Simulation with instruction ID and delay.
The first image shows the output following input.
The below image includes instruction ID, write done signals as well.
The above two images shows a 20 sec delay which processor takes to ammend the output change with respect to input change, first output is rising after input rises, second output falls after input falls.
To generate the netlist following commands were used
show wrapper
Below image shows the netlist generated with highlighted wrapper module.
To run Openlane following commands were used in the terminal.
make mount
./flow.tcl -interactive
package require openlane 0.9
prep -design project
Synthesis is the process of transfering higher level of abstraction(RTL) to implementable lower level of abstraction. It is the process of transforming RTL to gate-level netlist.
Synthesis = Translation + Logic Optimisation + Mapping
run_synthesis
chip area after synthesis is shown below
Floor planning is the first step in the physical design flow. Floor Planning is a quintessential step which decides the layout of the VLSI design. A good floorplan can be make implementation process (place, cts, route & timing closure) cake walk.
run_floorplan
Die Area details are shown below
Core Area details
-
Placement is the process of placing standard cell in the design, the tool determines the location of each standard cell on the die, the tool places these on basis of algorithm which it uses internally.
-
Placement does not just place the standard cells available in the synthesized netlist, it also optimizes the design, placement also determines the routability of the design.
-
Placement will be driven by the different criteria like timing driven, congestion driven and power optimisation.
run_placement
Clock Tree Synthesis is a technique for distributing the clock equally among all sequential parts of a VLSI design. The purpose of Clock Tree Synthesis is to reduce skew and delay.
run_cts
Path Details
- Routing is the stage after CTS, routing is nothing but connecting the various blocks with one another.
- Routing creates physical connections to all clock and the signal pins through metal interconnects
- After CTS, we have information about the exact location of placed cells, blockages, clock tree buffers/invertes I/O pins. The tool depends on this information to electrically complete all connections
- In routing stage, metal and visas are used to create the electrical connection in layout, to complete all connetions defined by the netlist.
run_routing
Given a Clock period of 100ns in Json file , setup slack we got after routing is 9.90ns
1
Max Performance = ------------------------
clock period - slack(setup)
Max Performance = 11.09 Mhz
I want to extend my appreciation to Kunal Ghosh(Founder & CEO VSD) for affording me the opportunity to learn about the ASIC design flow through his provision of high-quality educational materials.
I would also like to express my gratitude to Mayank Kabra(Founder, Chipcron Pvt. Ltd.) for his invaluable contributions and insights during the project's completion.
- https://lastminuteengineers.com/mq3-alcohol-sensor-arduino-tutorial/
- https://github.com/SakethGajawada/RISCV-GNU
- Pruthvi Parate, Colleague, IIIT Bangalore
- Bhargav DV, Colleague, IIIT Bangalore
- Koparthi Dinesh, IIIT Bangalore