There are some HW limitations in MT7688AN and known issues in the platforms. Here we summarize these information for reference:
Two I2C operation modes are not supported:
- Clock stretching
- Repeated start
- The max size of the I/O buffer of SPI is 16 bytes. If a data transmission larger than 16 bytes is issued, there will be an error reported.
- Full-duplex mode is not supported. Only half-duplex mode is supported.
- Mono (1 channel) is not supported.
- The supported sampling rates and data width are up to 192kHz / 24-bit.
AP mode is with better performance than Station mode.[Solved in firmware v0.9.4 and above] LinkIt Smart 7688 cannot be in both AP and Station mode at the same time (i.e. not available as a wireless repeater).[Supported in firmware v0.9.4 and above]
- Monitor mode is not supported.
- In Station mode, WPA-enterprise and WPA2-enterprise authentication protocols are not supported. WEP is not supported by default in OpenWrt due to its insecurity and it can be cracked in seconds.
USB 2.0 devices will be detected as USB 1.1 devices.[Solved in firmware v0.9.3 and above]
WAV recording with WM8960 is not supported yet.[Solved in firmware v0.9.3 and above]
.frequency()API in MRAA is not functional. Please use the
spi-configcommand to adjust the SPI working frequency. The following command sets the SPI working frequency to 7MHz:
# spi-config -d /dev/spidev32766.1 -s 7000000
For LinkIt Smart 7688, the MSB of a data transmission might be error. LinkIt Smart 7688 Duo does no have this issue.[Solved in firmware v0.9.3 and above]
- [v0.9.3] 16-bit data type is not functional. It can only work with 8-bit data type.
- GPIO 0 is occupied by the I2S driver and cannot be used as GPIO function.
UPM sensor support
- For the UPM compatibility of Seeed GROVE sensors on LinkIt Smart 7688, please refer to the compatibility list.