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pm:prj2025:eradu:alexandru.sima1512 [2025/05/29 23:37] alexandru.sima1512 [Hardware Design] Update components |
pm:prj2025:eradu:alexandru.sima1512 [2025/05/30 09:49] (current) alexandru.sima1512 [Flow] |
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| ===== Useful links ===== | ===== Useful links ===== | ||
| + | <note tip> | ||
| * Short demo: [[https://youtube.com/shorts/3NDd_IlYnws?feature=share]] | * Short demo: [[https://youtube.com/shorts/3NDd_IlYnws?feature=share]] | ||
| * Code repository: [[https://github.com/alx-sima/car-modulator]] | * Code repository: [[https://github.com/alx-sima/car-modulator]] | ||
| + | </note> | ||
| ===== Introduction ===== | ===== Introduction ===== | ||
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| ===== General description ===== | ===== General description ===== | ||
| - | {{:pm:prj2025:eradu:block_diagram_asima.png?200|}} | + | {{ :pm:prj2025:eradu:alexandru.sima1512:diagram.png?700 |}} |
| ===== Hardware Design ===== | ===== Hardware Design ===== | ||
| - | + | {{ :pm:prj2025:eradu:alexandru.sima1512:schematic.png?800 |}} | |
| - | {{:pm:prj2025:eradu:schematic_as.png?200|}} | + | |
| ==== List of components ==== | ==== List of components ==== | ||
| Line 43: | Line 42: | ||
| * VCC - 5V | * VCC - 5V | ||
| * GND - GND | * GND - GND | ||
| - | * AGND - GND | ||
| * R (stereo sound was too resource intensive) - PB1 (Arduino) | * R (stereo sound was too resource intensive) - PB1 (Arduino) | ||
| * LCD 1602: | * LCD 1602: | ||
| Line 76: | Line 74: | ||
| * Lab 2 - Interrupts | * Lab 2 - Interrupts | ||
| * Lab 4 - ADC | * Lab 4 - ADC | ||
| + | |||
| + | Lab concepts abstracted away by libraries: | ||
| + | * Lab 3 - Timers + PWM | ||
| + | * Lab 5 - SPI | ||
| * Lab 6 - I2C | * Lab 6 - I2C | ||
| Line 81: | Line 83: | ||
| * PC3 - input (for ADC) | * PC3 - input (for ADC) | ||
| * PD2 - input & pull-up (for button) | * PD2 - input & pull-up (for button) | ||
| + | * PD3 - output (Bluetooth receiver power) | ||
| ==== Flow ==== | ==== Flow ==== | ||
| - | **Synopsis**: A button is pressed to toggle the frequency selection. While in frequency selection mode, the //ADC// is continuously running and reading values from a voltage divider containing a potentiometer (knob), while the LCD is displaying the current selected value (read from the //ADC// on interrupts) and the transmitter is playing on the previous established frequency. While not selecting, the //ADC// is turned off in order to save energy, and the transmitter is playing on the established frequency (selected when the mode changes), while the LCD displays it. | + | **Synopsis**: A button is pressed to toggle the frequency selection, or held (>1s) to switch between playing audio from Bluetooth or the SD card. While in frequency selection mode, the //ADC// is continuously running and reading values from a voltage divider containing a potentiometer (knob), while the LCD is displaying the current selected value (read from the //ADC// on interrupts) and the transmitter is playing on the previous established frequency. While not selecting, the //ADC// is turned off in order to save energy, and the transmitter is playing on the established frequency (selected when the mode changes), while the LCD displays it. While playing audio from the SD card, the power supply is cut from the Bluetooth receiver, and ''wav'' files are played, in order, from the disk. A press of the button skips to the next song. |
| On setup, several registers are configured: | On setup, several registers are configured: | ||
| Line 100: | Line 103: | ||
| ===== Results ===== | ===== Results ===== | ||
| - | + | * The modulator manages to emit audio on the selected frequency at a reasonable quality. | |
| - | ===== Encountered challenges ===== | + | * Its range is about 10 meters, but it can be extended via an antenna (a simple wire will suffice). However, this is not usually desired as we do not want to interfere with others' radios. |
| + | * Audio played from a SD card is very noisy (because it is reconstructed using PWM). A low-pass filter or a dedicated DAC would have improved the quality. | ||
| + | ===== Challenges ===== | ||
| The initial plan was to use [[https://www.adafruit.com/product/1958|Adafruit Si4713]] as an FM transmitter. It was a circuit with more advanced capabilities (such as broadcasting text info about the radio "station"), and more (>0) documentation on the Internet. The order came late from China, and, to make matters worse, the chip was broken (wasn't even responding to a I2C address sweep). I couldn't find any replacement of the same model. | The initial plan was to use [[https://www.adafruit.com/product/1958|Adafruit Si4713]] as an FM transmitter. It was a circuit with more advanced capabilities (such as broadcasting text info about the radio "station"), and more (>0) documentation on the Internet. The order came late from China, and, to make matters worse, the chip was broken (wasn't even responding to a I2C address sweep). I couldn't find any replacement of the same model. | ||
