61 lines
2.3 KiB
Markdown
61 lines
2.3 KiB
Markdown
## UEXT overview
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the development boards so customer can choose which feature he want to use.
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UEXT (Universal-Extension-Connector) is board to board connector which support 3 serial communication interface, such as I2C, SPI, RS232.
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The combination of theese feature is supported by every decent microcontroller, this will enable broad choice to connect modules.
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UEXT gives you freedom to choose module that you want to use.
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!!! Notice
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As UEXT have RS232 and the Rx and Tx signals should be crossed we can say that UEXT on the board is with HOST; UEXT on the module is with SLAVE/DEVICE layout.
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## Pinout Table
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Helios64 provides UEXT on header P2 which following the UEXT standard, containing UEXT, SPI, and I2C connector.
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You can find the P2 header from the connector/interface list at [hardware overview](/helios64/hardware) page.
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Please find this location of UEXT header:
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The pinout of the above P2 header is decribed by following figures:
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Below is the detailed description of UEXT header pinout:
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| PIN | Port | Remarks |
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|-----|------|-------------|
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| 1 | 3.3V | |
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| 2 | GND | |
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| 3 | TXD (UART) | |
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| 4 | RXD (UART) | |
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| 5 | SCL (I2C) | |
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| 6 | SDA (I2C) | |
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| 7 | MISO (SPI) | |
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| 8 | MOSI (SPI) | |
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| 9 | SCK (SPI) | |
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|10 | SSEL (SPI) | |
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!!! Warning
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Please note the UEXT connector at Helios64 board doesn't provide the plastic covering, so be carefull with the header polarity!
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Make sure your device is correctly oriented before connecting!
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## SPI and I2C
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The implementation of SPI and I2C in the UEXT connector is follow similar convention in the Helios64 board. Please refer to this page:
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- [SPI](/helios64/hardware/)
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- [I2C](/helios64/I2C/)
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## Exception
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We have connected the UART bus from the RK3399 to the serial console in the USB-C, so there is no dedicated line of UART in the UEXT connector.
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The UART bus in this UEXT header is the parallel ones with the serial console.
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Therefore if you connect some module which might ***require dedicated serial UART line*** to the RK3399, this module ***will not function as expected***.
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!!! Notes
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Please note also, that GPS modules in UEXT format also will not work due to similar reason.
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## References
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https://www.olimex.com/Products/Modules/UEXT/
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