/ _____) _ | | ( (____ _____ ____ _| |_ _____ ____| |__ \____ \| ___ | (_ _) ___ |/ ___) _ \ _____) ) ____| | | || |_| ____( (___| | | | (______/|_____)_|_|_| \__)_____)\____)_| |_| ©2013 Semtech-Cycleo Lora Gateway HAL user manual ============================ 1. Introduction --------------- The Lora Gateway Hardware Abstraction Layer is a C library that allow you to use a Semtech Lora gateway hardware through a reduced number of high level C functions to configure the hardware, send and receive packets. The Semtech Lora gateway is a digital multi-channel multi-standard packet radio used to send and receive packets wirelessly using Lora or FSK modulations. 2. Components of the library ---------------------------- The library is composed of 5 modules: * loragw_hal * loragw_reg * loragw_spi * loragw_aux * loragw_gps The library also contains 4 test programs to demonstrate code use and check functionality. ### 2.1. loragw_hal ### This is the main module and contains the high level functions to configure and use the Lora gateway: * lgw_rxrf_setconf, to set the configuration of the radio channels * lgw_rxif_setconf, to set the configuration of the IF+modem channels * lgw_start, to apply the set configuration to the hardware and start it * lgw_stop, to stop the hardware * lgw_receive, to fetch packets if any was received * lgw_send, to send a single packet (non-blocking, see warning in usage section) * lgw_status, to check when a packet has effectively been sent For an standard application, include only this module. The use of this module is detailed on the usage section. ### 2.2. loragw_reg ### This module is used to access to the Lora gateway registers by name instead of by address: * lgw_connect, to initialise and check the connection with the hardware * lgw_disconnect, to disconnect the hardware * lgw_soft_reset, to reset the whole hardware by resetting the register array * lgw_reg_check, to check all registers vs. their default value and output the result to a file * lgw_reg_r, read a named register * lgw_reg_w, write a named register * lgw_reg_rb, read a name register in burst * lgw_reg_wb, write a named register in burst This module handles pagination, read-only registers protection, multi-byte registers management, signed registers management, read-modify-write routines for sub-byte registers and read/write burst fragmentation to respect SPI maximum burst length constraints. It make the code much easier to read and to debug. Moreover, if registers are relocated between different hardware revisions but keep the same function, the code written using register names can be reused "as is". If you need access to all the registers, include this module in your application. **/!\ Warning** please be sure to have a good understanding of the Lora gateway inner working before accessing the internal registers directly. ### 2.3. loragw_spi ### This module contains the functions to access the Lora gateway register array through the SPI interface: * lgw_spi_r to read one byte * lgw_spi_w to write one byte * lgw_spi_rb to read two bytes or more * lgw_spi_wb to write two bytes or more Please *do not* include that module directly into your application. **/!\ Warning** Accessing the Lora gateway register array without the checks and safety provided by the functions in loragw_reg is not recommended. ### 2.4. loragw_aux ### This module contains a single host-dependant function wait_ms to pause for a defined amount of milliseconds. The procedure to start and configure the Lora gateway hardware contained in the loragw_hal module requires to wait for several milliseconds at certain steps, typically to allow for supply voltages or clocks to stabilize after been switched on. An accuracy of 1 ms or less is ideal. If your system doesn't allow that level of accuracy, make sure that the actual delay is *longer* that the time specified when the function is called (ie. wait_ms(X) *MUST NOT* before X milliseconds under any circumstance). If the minimum delays are not guaranteed during the configuration and start procedure, the hardware might not work at nominal performance. Most likely, it will not work at all. ### 2.5. loragw_gps ### This module contains functions to synchronize the concentrator internal counter with an absolute time reference, in our case a GPS satellite receiver. The internal concentrator counter is used to timestamp incoming packets and to triggers outgoing packets with a microsecond accuracy. In some cases, it might be useful to be able to transform that internal timestamp (that is independent for each concentrator running in a typical networked system) into an absolute UTC time. In a typical implementation a GPS specific thread will be called, doing the following things after opening the serial port: * blocking reads on the serial port (using system read() function) * parse NMEA sentences (using lgw_parse_nmea) And each time an RMC sentence has been received: * get the concentrator timestamp (using lgw_get_trigcnt, mutex needed to protect access to the concentrator) * get the UTC time contained in the NMEA sentence (using lgw_gps_get) * call the lgw_gps_sync function (use mutex to protect the time reference that should be a global shared variable). Then, in other threads, you can simply used that continuously adjusted time reference to convert internal timestamps to UTC time (using lgw_cnt2utc) or the other way around (using lgw_utc2cnt). 3. Software dependencies ------------------------ The library is written following ANSI C conventions but using C99 explicit length data type for all data exchanges with hardware and for parameters. The loragw_aux module contains POSIX dependant functions for millisecond accuracy pause. For embedded platforms, the function could be rewritten using hardware times. All modules use the fprintf(stderr,...) function to display debug diagnostic messages if the DEBUG_xxx is set to 1 in library.cfg Depending on config, SPI module needs LibMPSSE to access the FTDI SPI-over-USB bridge. Please go to that URL to download that library: http://code.google.com/p/libmpsse/ The code was tested with version 1.3 of LibMPSSE: http://libmpsse.googlecode.com/files/libmpsse-1.3.tar.gz SHA1 Checksum: 1b994a23b118f83144261e3e786c43df74a81cd5 That library has some dependencies itself, please read the installation instructions. 4. Hardware dependencies ------------------------ ### 4.1. Hardware revision ### The loragw_reg and loragw_hal are written for a specific version on the Semtech hardware (IP and/or silicon revision). All relevant details are contained in the VERSION.TXT file. The library will not work if there is a mismatch between the hardware version and the library version. You can use the test program test_loragw_reg to check if the hardware registers match their software declaration. ### 4.2. SPI communication ### loragw_spi contains 4 SPI functions (read, write, burst read, burst write) that are platform-dependant. The functions must be rewritten depending on the SPI bridge you use: * SPI master matched to the Linux SPI device driver (provided) * SPI over USB using FTDI components (provided) * native SPI using a microcontroller peripheral (not provided) Edit library.cfg to chose which SPI physical interface you want to use. You can use the test program test_loragw_spi to check with a logic analyser that the SPI communication is working ### 4.3. GPS receiver (or other GNSS system) ### To use the GPS module of the library, the host must be connected to a GPS receiver via a serial link (or an equivalent receiver using a different satellite constellation). The serial link must appear as a "tty" device in the /dev/ directory, and the user launching the program must have the proper system rights to read and write on that device. Use `chmod a+rw` to allow all users to access that specific tty device, or use sudo to run all your programs (eg. `sudo ./test_loragw_gps`). In the current revision, the library only reads data from the serial port, expecting to receive NMEA frames that are generally sent by GPS receivers as soon as they are powered up. The GPS receiver __MUST__ send RMC NMEA sentences (starting with "$GRMC") shortly after sending a PPS pulse on to allow internal concentrator timestamps to be converted to absolute UTC time. If the GPS receiver sends a GGA sentence, the gateway 3D position will also be available. The PPS pulse must be sent to the pin 22 of connector CONN400 on the Semtech FPGA-based nano-concentrator board. Ground is available on pins 2 and 12 of the same connector. The pin is loaded by an FPGA internal pull-down, and the signal level coming in the FPGA must be 3.3V. Timing is captured on the rising edge of the PPS signal. 5. Usage -------- ### 5.1. Setting the software environment ### For a typical application you need to: * include loragw_hal.h in your program source * link to the libloragw.a static library during compilation * link to the librt library due to loragw_aux dependencies (timing functions) * link to the libmpsse library if you use a FTDI SPI-over-USB bridge For an application that will also access the concentrator configuration registers directly (eg. for advanced configuration) you also need to: * include loragw_reg.h in your program source ### 5.2. Using the software API ### To use the HAL in your application, you must follow some basic rules: * configure the radios path and IF+modem path before starting the radio * the configuration is only transferred to hardware when you call the *start* function * you cannot receive packets until one (or +) radio is enabled AND one (or +) IF+modem part is enabled AND the gateway is started * you cannot send packets until one (or +) radio is enabled AND the gateway is started * you must stop the gateway before changing the configuration A typical application flow for using the HAL is the following: loop { } **/!\ Warning** The lgw_send function is non-blocking and returns while the Lora gateway is still sending the packet, or even before the packet has started to be transmitted if the packet is triggered on a future event. While a packet is emitted, no packet can be received (limitation intrinsic to most radio frequency systems). Your application *must* take into account the time it takes to send a packet or check the status (using lgw_status) before attempting to send another packet. Trying to send a packet while the previous packet has not finished being send will result in the previous packet not being sent or being sent only partially (resulting in a CRC error in the receiver). ### 5.3. Debugging mode ### To debug your application, it might help to compile the loragw_hal function with the debug messages activated (set DEBUG_HAL=1 in library.cfg). It then send a lot of details, including detailed error messages to *stderr*. *EOF*