OLIMEX© 2015
A20-SOM user's manual
Consider the table on the previous page when connecting the USB-SERIAL-CABLE-F, remember
to refer to the wire color code. The RX line of the cable (GREEN wire) should go to TX line of the
target board; the TX line of the cable (RED wire) should go to the RX line of the target board. The
BLUE wire should go to the target's GND line.
6.3 MicroSD card connector
The micro SD card slot is primarily used for booting the operating system.
The board works with micro SDHC cards up to 32GB of storage.
As a general precaution be careful with the SD cards you purchase. There is a big percentage of
fake cards due to the low effort required to counterfeit popular brands and the big demand for SD
cards worldwide. When in doubt – try the same operation with another card from another brand.
Olimex sells microSD cards with Linux or Android images, that have been tested – please refer to
chapter “2.2 Requirements”. Of course, if you already have a large enough microSD card you can
download the official Linux image from the wiki pages:
https://www.olimex.com/wiki/A20-SOM
.
When removing the card, please make sure that you release it from the connector by pushing and
NOT by pulling the card directly (this can damage both the connector and the microSD card).
6.3.1 SD/MMC slot
The schematic related to the SD/MMC (microSD connector) is shown below.
SD/MMC slot is a microSD card slot connector,
located on the top of the board.
This slot is typically used for booting the OS, due
to the larger capacities of the microSD cards
(compared to SD or MMC cards). It is suggested to
have an SD card with a proper Linux/Android
image especially if you have ordered a version of
the board without NAND memory. It is
recommended to use Class 10 (10MByte/sec) card
for faster read/write operations, since lower class
cards (especially higher capacity ones) might slow
down the whole system.
You can also find the table with the pinout of the
microSD connector on the next page.
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