## FPC BM-Lite example application

This is a port of [FPC BM-Lite Development Kit](https://www.fingerprints.com/solutions/access/bm-lite-development-kit/ "BM-Lite Development Kit") to Nordic nRF52840-DK development board. FPC BM-Lite module connected to the dev board by SPI interface.

There are 3 main folders in the project:
- [BMLite_example](BMLite_example) - main HW-independed application
- [HAL_Driver](HAL_Driver) - implementation of HW-dependent functions

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### Platform-independent interface functions

Platform-independent interface implemented in [platform.c](BMLite_example/src/platform.c)

| Platform function | Description  |
| :-------- | :-------- |
| bool **platform_init**(uint32_t speed_hz) |  Initilalizes hardware |
| void **platform_bmlite_reset**(void) | Implements BM-Lite HW Reset |
| fpc_bep_result_t **platform_bmlite_send**(uint16_t size, const uint8_t *data, uint32_t timeout, void *session) | Send data packet to FPC BM-LIte |
| fpc_bep_result_t **platform_bmlite_receive**(uint16_t size, uint8_t *data, uint32_t timeout, void *session) | Receive data packet from FPC BM-LIte. If timeout = **0**, the function will wait for data from BM-Lite indefinitely. The waiting loop will be breaked if **hal_check_button_pressed()** returns non-zero value. It is recommended to do HW or SW reset of BM-Lite if **platform_bmlite_receive()** returns **FPC_BEP_RESULT_TIMEOUT** in order to return is into known state. |

Currently **platform_bmlite_send()** and **platform_bmlite_receive()** are implemented for SPI interface. For UART interface there is no need to wait for **IRQ** pin ready. However because in UART mode there is no signal from FPC-BM-LIte that it will send data, I would recommend to use UART interrupt or DMA to receive data from UART and store it to a separate buffer and read data in **platform_bmlite_receive()** from that buffer. Activation UART data reading only inside **platform_bmlite_receive()** could lead to loosing some incoming data and causing HCP protocol errors.

------------

### HAL implementation

For porting the project to a new microcontroller, all functions from [bmlite_hal.h](BMLite_example/inc/bmlite_hal.h) should be implemented.

#### Functions must be implemented: 

|  HAL Function |  Description |
| :------------ | :------------ |
| void **hal_board_init**(uint32_t speed_hz) |  Initialize GPIO, System timer, SPI  |
| void **hal_bmlite_reset**(bool state) |  Activate/Deactivate BM-Lite **RST_N** pin (***Active Low***) |
| fpc_bep_result_t **hal_bmlite_spi_write_read**(uint8_t *write, uint8_t *read, size_t size, bool leave_cs_asserted) |  SPI data exchange |
| bool **hal_bmlite_get_status**(void) | Return status of BM-Lite **IRQ** pin (***Active High***) |
| void **hal_timebase_init**(void) |  Initialize system clock with 1 msec tick |
| uint32_t **hal_timebase_get_tick**(void) | Read currect system clock value |
| void **hal_timebase_busy_wait**(uint32_t ms) | Delay for **ms** msec |

#### Optional functions for  implementing user interface in BM-Lite example application:

|  HAL Function |  Description |
| :------------ | :------------ |
| uint32_t **hal_get_button_press_time**(void) | How long UI button was pressed last time. Also it should reset button pressed time counter |
| uint32_t **hal_check_button_pressed**(void) | Used for breaking waiting in **platform_bmlite_receive()** if returns non-zero |
| void **hal_set_leds**(platform_led_status_t status, uint16_t mode) | Set LED(s) state according to status and mode. |

------------

### Some notes about FPC BM-Lite HW interface

- BM-Lite support both UART and SPI communication interface. BM-Lite automatically detects the specific communication interface in use. However, it is not possible to use both interfaces at the same time! 
- **IRQ** pin is used in SPI mode only as FPC BM-Lite Ready-to-Transmit signal. The module set it to **High** when it has some data to send and set it to **Low** when data packet is sent.

