BL652 Development Kit
User Guide
Embedded Wireless Solutions Support Center:
http://ews-support.lairdtech.com
www.lairdtech.com/bluetooth
28
© Copyright 2016 Laird. All Rights Reserved
Americas: +1-800-492-2320
Europe: +44-1628-858-940
Hong Kong: +852 2923 0610
The on-board temperature sensor (TI LM20BIM7 -
www.ti.com/lit/ds/symlink/lm20.pdf
) has an Analogue output
that can be connected to BL652 module pin SIO_3; but since the LM20BIM7 has an analogue output, the BL652
module SIO_3 digital pin (DIO) must be configured as AIN analogue input (ADC). To configure the SIO_3 pin from
DIO pin to Alternate function AIN, see the example file “ts.temperature.sensor.sb” in the GitHub smartBASIC
sample applications repository on the BL652 product page at
https://github.com/LairdCP/BL652-Applications
Key specifications of the LM20BIM7 are as follows in
Table 9
.
Table 9: LM20BIM7 Specifications
Output type
Analogue output
Accuracy at 30ºC
±1.5ºC ±4ºC (max)
Accuracy at 40ºC to +85ºC
approx. ±2.5ºC ±5ºC (max)
Power supply voltage range
+2.4 V to 5.5 V
Current Drain
10 uA (max)
Output impedance
160 Ohms (max)
The LM20BIM7 datasheet states the relationship of Temperature (T) to Voltage output (Vo) can be
approximated as a linear equation (for temperature range of -40ºC to +85ºC):
Vo(mV) = -11.67mV/ºC x T + 1858.3
gives the following calculated Vo versus temperature:
Table 10: LM20BIM7 Temperature to Voltage Output relationship
Temperature (T)
Typical Voltage
+80ºC
+924.7mV
+70ºC
+1041.4mV
+60ºC
+1158.1mV
+50ºC
+1274.8mV
+40ºC
+1391.5mV
+30ºC
+1508.2mV
+20ºC
+1624.9mV
+10ºC
+1741.6mV
+0ºC
+1858.2mV
-10ºC
+1975.0mV
-20ºC
+2091.7mV
-30ºC
+2208.4mV
8.3.2
I2C Sensor (RTC Chip)
The I2C RTC chip (U16) allows the BL652 I2C interface to be tested. The output of the RTC chip (U16) is on the
I2C bus and is by default connected to the BL652 module via jumpers on J13 pins 2-3 and J14 pins 2-3.
Table 11: I2C RTC chip BL652 I2C signal mappings
I2C RTC EEPROM (U16)
BL652 module (U5) SIO
Comments
(U16 pin6) RTC_SCL
(U5 pin38) SIO_27
Fit jumper on J13 pins 2-3 to select
(U16 pin5) RTC_SDA
(U5 pin37) SIO_26
Fit jumper on J14 pins 2-3 to select
