NB-IoT Module Series
BC66 Hardware Design
BC66_Hardware_Design 29 / 50
Please visit vendors
’ websites to select a suitable RS-232 transceiver, such as: http://www.exar.com and
http://www.maximintegrated.com.
1. Transistor circuit solution is not suitable for applications with high baud rates exceeding 460Kbps.
2.
“
” represents the test point of UART interfaces. It is also recommended to reserve the test points of
VBAT and PWRKEY, for convenient firmware upgrade and debugging when necessary.
3.9. SPI Interface
BC66 provides one SPI master interface. The following table shows the pin definition of SPI interface.
Table 10: Pin Definition of SPI Interface
The module provides a 1.8V SPI interface. A level translator between the module and host should be
used if the application is equipped with a 3.3V processor or device interface. A voltage level translator that
supports SPI data rate is recommended. The following figure shows a reference design.
VCCA
VCCB
OE
A1
A2
A3
A4
GND
B1
B2
B3
B4
VDD_EXT
CS_SPI
SCLK_SPI
MOSI_SPI
0.1uF
0.1uF
CS_SPI
SCLK_SPI
MISO_SPI
MOSI_SPI
VDD
Translator
Module
DTE
MISO_SPI
Figure 18: SPI Interface Reference Circuit with Translator Chip
Pin Name Pin No.
I/O
Description
Comment
SPI_MISO
3
DI
Master input and slave output of SPI interface
1.8V power domain
SPI_MOSI
4
DO
Master output and slave input of SPI interface
SPI_SCLK
5
DO
Clock signal of SPI interface
SPI_CS
6
DO
Chip selection of SPI interface
NOTES
