TFmini, UART to I2C, Switching Value. STM32F030F4P6 is I2C Slave. Arduino is I2C Master.
Schematic diagram: TFmini2JSRZ_SCH.pdf
PCB Gerber: TFmini2JSRZ Gerber Files
Instructions for making boards: TFmini2JSRZ制板说明.xls, Note that the board thickness is 1.0mm.
List of components: TFmini2JSRZ _BOM.xls, All components can be purchased in 立创商城, 1688或者 淘宝 .
After testing, need to get rid of D1 and changed to 0 Ω resistance, otherwise, TFmini cannot start normally under 3.9v.
The appearance of finished boards:
HOUT is the switch pin, push pull output 3.3v level. If you want to connect 5V level, you can modify the program, change HOUT pin to open leakage output, pull up 10K resistance to 5V.
The output of TFmini ranging beyond the range threshold is low (0V), while the output below the range threshold is high (3.3v).
In order to prevent the output from jitter around the threshold, in fact, when the TFmini distance exceeds the distance threshold +15cm, the output is low (0V, the indicator is D3 on), while when the distance threshold is lower than +5cm, the output is high (3.3v, the indicator is D3 off).
The threshold value of switch quantity (HOUT) can be set by dialing code switch (dial On, 1 above) and potentiometer:
| Dial switch | threshold |
|---|---|
| 00(Off Off) | Through the potentiometer adjustment (0.3~12m), the clockwise threshold increases, observe the LED indicator light on and off to set the appropriate threshold |
| 01(Off On) | 2m |
| 10(On Off) | 3m |
| 11(On On) | 5m |
You can directly use j-link or st-link to burn B files under A.
The program for the TFmini2JSRZ board is TFmini2JSRZ_Slave. You can directly use J-LINK or ST-LINK to burn TFmini2JSRZ_Slave.hex files under TFmini2JSRZ\TFmini2JSRZ_Slave\MDK-ARM\TFmini2JSRZ_Slave .
I2C Slave address is 0x59(89), write address is 178, read address is 179(0x59 << 1 + 1). Master sends 0x42(66) to Slave(TFmini2JSRZ), Slave(TFmini2JSRZ) returns 4 bytes each time, namely 8 bits low of distance, 8 bits high of distance, 8 bits low of strength, 8 bits high of strength.
The I2C master-slave communication data captured by the logic analyzer are as follows:
Take Arduino as an example of I2C host, and the connection relationship is as follows:
| TFmini2JSRZ | Arduino |
|---|---|
| GND | GND |
| SCL | SCL |
| SDA | SDA |
The reading example is as follows:
#include <Wire.h>
#define I2C_SLAVE_ADDR1 0x59
typedef struct {
char distanceLow;
char distanceHigh;
int distance;
char strengthLow;
char strengthHigh;
int strength;
boolean receiveComplete;
}TFmini;
TFmini TFminiOne = {0, 0, 0, 0, 0, 0, false};
void setup() {
Wire.begin(); // join i2c bus (address optional for master)
Serial.begin(115200);
}
unsigned long lastTime = millis();
unsigned int count = 0;
unsigned int frequency = 0;
void loop() {
if((millis() - lastTime) % 10 == 0) {
delay(1); //I2C Communication < 1ms. It will be run twice per 10 milliseconds if not delay(1)
Wire.beginTransmission(I2C_SLAVE_ADDR1);
Wire.write(byte(0x42));
Wire.endTransmission();
Wire.requestFrom(I2C_SLAVE_ADDR1, 4); // request 4 bytes from slave device
if(4 <= Wire.available()) {
TFminiOne.distanceLow = Wire.read();
TFminiOne.distanceHigh = Wire.read();
TFminiOne.strengthLow = Wire.read();
TFminiOne.strengthHigh = Wire.read();
TFminiOne.receiveComplete = true;
}
}
if(TFminiOne.receiveComplete == true) {
TFminiOne.receiveComplete = false;
++count;
TFminiOne.distance = TFminiOne.distanceLow + TFminiOne.distanceHigh * 256;
TFminiOne.strength = TFminiOne.strengthLow + TFminiOne.strengthHigh * 256;
Serial.print(TFminiOne.distance);
Serial.print("cm\t");
Serial.print("strength: ");
Serial.print(TFminiOne.strength);
Serial.print("\t");
Serial.print(frequency);
Serial.println("Hz");
}
if(millis() - lastTime > 999) {
lastTime = millis();
frequency = count;
count = 0;
}
}
Data are shown in the figure. The left is the actual distance, the middle is the signal quality, and the right is the communication frequency:
