Some people tried already to get this RP2040 working with other software - e.g. Micropython or Arduino, but I never heard someone getting it working, so I tried my luck - this is the whole journey from start to finish. Spoiler, it is now working and you can find the example code at the end with Arduino-Pico and RadioLib now fully supporting this module :).<\/p>\n
Pinout<\/h3>\n
The most important thing was trying to figure out the internal wiring of the RP2040 to the SX1262 - while RAK did not offer complete schematics, they at least revealed parts of it<\/a> after asking in the forums<\/a> :).<\/p>\n To sum up:<\/p>\n To get this to work, you can take the legendary Earle F. Philhower's Arduino Pico repo<\/a>, use the normal RPi Pico board and overwrite the SPI1 positions like so:<\/p>\n however, to make it easier I put up a PR<\/a> to directly change those pinouts and integrate the RAKwireless RAK11300 proper into the arduino-pico framework.<\/p>\n Lets get to the SX1262 library and the implementation of the LoRaWAN communication schema: The most weird thing is still the GPIO 25 for me, the mentioned Antenna switch power. It might be all thats needed to put this port as output and put it on high to supply power whenever someone wants to receive\/transmit - but I am not really sure yet. I have not found any evidence and I feel something with the join event in the RadioLib is still off as other people<\/a> also saw issues - so there are probably two different problems right now.<\/p>\n To understand the whole idea better, I opened up one RAK11300 and put it under the microscope. Sadly my microscope camera ain't really good, so the picture quality is a bit hit and miss, but as there are no pictures at all on the internet, I thought it might be useful for someone. <\/p>\n Some details:<\/p>\n So it looks like the RP2040 PIN 25 could be really the "power supply" for that switch, while the DIO2 of the SX1262 would be changing the switch to either supply the RX or TX chains to the antenna output, however I am not that sure.<\/p>\n So, without anymore addition, here are the pictures, sorry for the bad quality.<\/p>\n If you have any infos to help on the quest, please let me know :).<\/p>\n Looking at the lora_rak11300_init, we can quickly find out that the GPIO 25 is used as power to the antenna switch, e.g. switching on the use of the antenna. Its important to see that TXEN=-1, so RXEN and TXEN are not used to determine the direction (e.g. if sending or receiving, but this is done by DIO2\/directly by the SX1262 module. The use of RXEN\/GPIO25 is purely for powering the Antenna switch:<\/p>\n ( https:\/\/github.com\/beegee-tokyo\/SX126x-Arduino\/blob\/fe6178f82d81e6509a5352f1d2aa85e433e19a7a\/src\/boards\/mcu\/board.cpp#L239C25-L239C25<\/a> )<\/p>\n If we dig a bit deeper, we will find the SX126xIoInit ( https:\/\/github.com\/beegee-tokyo\/SX126x-Arduino\/blob\/ca879479b25071c568ded9a60f7c060f10c7791a\/src\/boards\/sx126x\/sx126x-board.cpp#L49<\/a> )<\/p>\n This also shows that the GPIO25 is used only as antenna switch power and is configured as output, but still in "low" mode, e.g. the power switch is off.<\/p>\n In all instances of the Antenna used or the TX\/RX channels ( SX126xAntSwOn, SX126xAntSwOff, SX126xRXena, SX126xTXena - https:\/\/github.com\/beegee-tokyo\/SX126x-Arduino\/blob\/ca879479b25071c568ded9a60f7c060f10c7791a\/src\/boards\/sx126x\/sx126x-board.cpp#L496-L555<\/a> ) we can see that the GPIO25 is pulled high, e.g powers on the Antenna Switch - and powers down after sending. It does not make a difference if TX or RX is needed, its always HIGH\/ON when the antenna is used and LOW\/OFF when its not. Probably to preserve energy. So basically, we would need to always set GPIO25 as output and pull it high when we need to use the module.<\/p>\n I got TTN working, however Chirpstack proved to be difficult. Reason was the error "ERROR chirpstack::uplink: Deduplication error error=Unknown data-rate: Lora(LoraDataRate { spreading_factor: 7, bandwidth: 125000, coding_rate: \u201c4\/7\u201d })" reason for that was that RadioLib accidently tries to drive EU868 packets with 4\/7 instead of 4\/5 coding rate - so these packets are thrown away right away ( https:\/\/forum.chirpstack.io\/t\/error-unknown-data-rate-on-eu868-with-coding-rate-4-7\/16109<\/a> ). I made a PR ( https:\/\/github.com\/jgromes\/RadioLib\/pull\/865<\/a> ) to fix that issue. There is also an error in the LoRaWAN example as handled by this PR ( https:\/\/github.com\/jgromes\/RadioLib\/pull\/866<\/a> ). With that we can finally join TTN and Chirpstack v4 servers! What is still a problem, is re-connecting: Trying to restore a connection ends with an issue -1101 in RadioLib, seems to be what was described beforehand in https:\/\/github.com\/jgromes\/RadioLib\/issues\/858<\/a>. Lets see if we find something. Other than that, its looking so much better already :)\/<\/p>\n RadioLib has accepted the PR and the needed commits are now in the main branch. Earle has now released arduino-pico 3.6.1 which does include my contribution and adds the RAK11300 as its own board to his awesome Arduino Core ( https:\/\/github.com\/earlephilhower\/arduino-pico\/releases\/tag\/3.6.1<\/a> ). You can download it right now via the Arduino Board Manager. So we just need for the latest RadioLib to drop :).<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/rak11300_schematic.png?resize=207%2C300&ssl=1\")
<\/a><\/p>\nThe antenna switch direction is controlled by the SX1262 itself through DIO2.\nThe antenna switch power is controlled with GPIO25\nIt uses an TCXO<\/code><\/pre>\nuint32_t lora_rak11300_init(void)\n{\n _hwConfig.CHIP_TYPE = SX1262; \/\/ Chip type, SX1261 or SX1262\n _hwConfig.PIN_LORA_SCLK = 10; \/\/ LORA SPI CLK\n _hwConfig.PIN_LORA_MOSI = 11; \/\/ LORA SPI MOSI\n _hwConfig.PIN_LORA_MISO = 12; \/\/ LORA SPI MISO\n _hwConfig.PIN_LORA_NSS = 13; \/\/ LORA SPI CS\n _hwConfig.PIN_LORA_RESET = 14; \/\/ LORA RESET\n _hwConfig.PIN_LORA_BUSY = 15; \/\/ LORA SPI BUSY\n _hwConfig.RADIO_TXEN = -1; \/\/ LORA ANTENNA TX ENABLE (e.g. eByte E22 module)\n _hwConfig.RADIO_RXEN = 25; \/\/ LORA ANTENNA RX ENABLE (e.g. eByte E22 module)\n _hwConfig.USE_DIO2_ANT_SWITCH = true; \/\/ LORA DIO2 controls antenna\n _hwConfig.USE_DIO3_TCXO = true; \/\/ LORA DIO3 controls oscillator voltage (e.g. eByte E22 module)\n _hwConfig.USE_DIO3_ANT_SWITCH = false; \/\/ LORA DIO3 controls antenna (e.g. Insight SIP ISP4520 module)\n _hwConfig.PIN_LORA_DIO_1 = 29; \/\/ LORA DIO_1\n _hwConfig.USE_RXEN_ANT_PWR = true; \/\/ RXEN is used as power for antenna switch\n#ifdef RAK11310_PROTO\n _hwConfig.USE_LDO = true; \/\/ True on RAK11300 prototypes because of DCDC regulator problem\n#else\n _hwConfig.USE_LDO = false;\n#endif<\/code><\/pre>\n\n
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RP2040<\/h3>\n
SPI1.setCS(13);\nSPI1.setSCK(10);\nSPI1.setTX(11);\nSPI1.setRX(12);\nSPI1.begin(false);<\/code><\/pre>\nSX1262<\/h3>\n
\nLuckily, Jan Grome\u0161, maintainer of the awesome RadioLib<\/a> decided to implement LoRaWAN support - and the SX1262 modules. I tried to get everything working, however, there seem to be some minor issues. His library does detect the SX1262, however, I am not able to join TTN with it. The issue ticket is currently open here<\/a>.<\/p>\nGetting further<\/h3>\n
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GPIO25 | Antenna | DIO2(?)\n 259\n 128\n* VR_PA\/RFO | GND | RFI_N\/RFI_P<\/code><\/pre>\nPhotos<\/h3>\n
![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00001.jpg?resize=300%2C169&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00002.jpg?resize=300%2C169&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00003.jpg?resize=300%2C169&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00004.jpg?resize=300%2C169&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00005.jpg?resize=300%2C169&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00006.jpg?resize=300%2C169&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00007.jpg?resize=232%2C300&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00008.jpg?resize=233%2C300&ssl=1\")
<\/a><\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.nico-maas.de\/wordpress\/wp-content\/uploads\/RAK11300_00009.jpg?resize=226%2C300&ssl=1\")
<\/a><\/p>\nUpdate to the Antenna Switch \/ GPIO25 (@2023-11-03 17:08)<\/h3>\n
_hwConfig.RADIO_TXEN = -1; \/\/ LORA ANTENNA TX ENABLE (e.g. eByte E22 module)\n _hwConfig.RADIO_RXEN = 25; \/\/ LORA ANTENNA RX ENABLE (e.g. eByte E22 module)\n _hwConfig.USE_RXEN_ANT_PWR = true; \/\/ RXEN is used as power for antenna switch\n _hwConfig.USE_DIO2_ANT_SWITCH = true; \/\/ LORA DIO2 controls antenna<\/code><\/pre>\n \/\/ Use RADIO_RXEN as power for the antenna switch\n if (_hwConfig.USE_RXEN_ANT_PWR)\n {\n if (_hwConfig.RADIO_TXEN != -1)\n pinMode(_hwConfig.RADIO_TXEN, INPUT);\n pinMode(_hwConfig.RADIO_RXEN, OUTPUT);\n digitalWrite(_hwConfig.RADIO_RXEN, LOW);\n }<\/code><\/pre>\nUpdate to RadioLib (@2023-11-03 20:29)<\/h3>\n
Update to RadioLib (@2023-11-04 16:25)<\/h3>\n
\n
static const uint32_t rfswitch_pins[] = { 25, RADIOLIB_NC, RADIOLIB_NC };\nstatic const Module::RfSwitchMode_t rfswitch_table[] = {\n{MODE_IDLE, { LOW }},\n{MODE_RX, { HIGH }},\n{MODE_TX, { HIGH }},\nEND_OF_MODE_TABLE,\n};\n(...)\nradio.setRfSwitchTable(rfswitch_pins, rfswitch_table); \/\/ must be called before begin!\nradio.begin();<\/code><\/pre>\n<\/li>\nUpdate to RadioLib (@2023-11-12 14:02)<\/h3>\n
\nBoth RadioLib and Arduino-Pico have not yet posted a new release version, so if you want to use the tech right now, you need to install the current main git branches.<\/p>\nUpdate to Arduino-Pico (@2023-11-22)<\/h3>\n
Update to RadioLib (@2023-11-29)<\/h3>\n