The MCA implements three UARTs in its firmware (starting from firmware version 0.13).
When enabled, the serial ports are listed as /dev/ttyMCAx
.
The configuration options are limited to:
-
Baud rates: from 1200 up to 230400 bps. Note that for baudrates higher than 57600, flow control is recommended.
-
Parity: none, even, or odd.
-
Stop Bits: 1 or 2.
-
Hardware flow-control through CTS and RTS lines.
Manual handling of the RTS and CTS lines through standard TIOCMGET and TIOCMSET ioctls is not supported. |
MCA IO pins selection
You can only use certain IO pins for the RX/TX lines of each UART:
MCA UART | IOs for RX | IOs for TX | IOs for CTS | IOs for RTS | |
---|---|---|---|---|---|
UART0 |
MCA_IO9 |
MCA_IO10, MCA_IO13 |
any |
any |
|
UART1 |
MCA_IO11, MCA_IO15 |
MCA_IO16 |
any |
any |
|
UART2 |
MCA_IO2, MCA_IO17 |
MCA_IO1, MCA_IO18 |
any |
any |
On the ConnectCore 8M Mini Development Kit:
-
MCA UART2 is routed to the XBee socket with the following IO pins:
-
RX on MCA_IO2
-
TX on MCA_IO1
-
CTS on MCA_IO3
-
RTS on MCA_IO4
-
Kernel configuration
You can manage the MCA UART driver support through the following kernel configuration option:
-
Digi ConnectCore Micro Controller Assist assist UART (
CONFIG_SERIAL_MCA
)
This option is enabled as built-in on the default ConnectCore 8M Mini kernel configuration file.
Kernel driver
The MCA UART driver is located at:
File | Description |
---|---|
UART driver for MCA |
Device tree bindings and customization
The MCA UART device tree binding is documented at Documentation/devicetree/bindings/serial/digi,mca-uart.txt
.
Example: MCA UART on the ConnectCore 8M Mini Development Kit
UART controller inside the MCA
The MCA UARTs are defined in the ConnectCore 8M Mini device tree.
mca_cc8m: mca@63 {
...
mca_uart: uart {
compatible = "digi,mca-cc8m-uart";
#address-cells = <1>;
#size-cells = <0>;
mca_uart0: serial@0x900 {
reg = <0x900>;
index = <0>;
};
mca_uart1: serial@0x920 {
reg = <0x920>;
index = <1>;
};
mca_uart2: serial@0x940 {
reg = <0x940>;
index = <2>;
};
};
};
MCA UART enabling
The board device tree defines the pins to be used for each of the MCA UART lines.
&mca_uart {
status = "okay";
/* Uncomment to enable MCA UART0. Assign the IO pins (see bindings) */
// mca_uart0: serial@0x900 {
// iopins-names = "rx", "tx";
// iopins = <9 10>;
// };
/* Uncomment to enable MCA UART1. Assign the IO pins (see bindings) */
// mca_uart1: serial@0x920 {
// iopins-names = "rx", "tx";
// iopins = <11 16>;
// };
/* UART connected to XBee socket */
mca_uart2: serial@0x940 {
iopins-names = "rx", "tx", "cts", "rts";
iopins = <2 1 3 4>;
};
};
Power management
MCA UART0 and MCA UART1 are low-power UARTs and, as such, are capable of waking the system from suspend and from power-off states.
Wake from suspend
To allow an MCA UART to resume the system from suspend when a character is received (and not lose data), run the following command:
# echo enabled > /sys/class/tty/ttyMCAx/power/wakeup
where x is the UART index, starting at 0.
An application must be reading from the device or the system will not wake up when a character is received. |
Power on the system
To allow an MCA UART to power on the system, run the following command:
# echo enabled > /sys/class/tty/ttyMCAx/power_extra_opts/power_on_rx
where x is the UART index, starting at 0.
The UART remains with the latest configuration of baud rate, parity, and stop bits.
An application must be reading from the device or the system will not wake up when a character is received. This setting does not persist across reset or power cycles, so you must enable it each time. |