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--- microcontrollers:common_communication_types [2024/10/30 19:02] – [UART (Universal Asynchronous Receiver-Transmitter)] ibchadmin
+++ microcontrollers:common_communication_types [2024/10/30 19:21] (current) – ibchadmin
@@ Line 41: / Line 41: @@
 {{ :microcontrollers:uart1.png?direct&400 |}}
+  * UART transmits bits sequentially by pulling the UART line low for a fixed amount of time determined by the baud rate. T
+  * The UART line when idle is high at the I/O level, 3.3V or whatever the VCC of the MSP430 is set.
+==== UART Configuration ====
+  * Refer to the datasheet to select the available module for UART.
+  * Configure the  2 Pins (tx and rx) for UART by configuring PxSEL0 and PxSEL1 to select the UART function for those pins. (refer to the datasheet of your microcontroller to knew what value you should assign for each register).
+	example using UCA0 module for MSP430FR5994
+Config pins for UART operation P2.0 -> UCA0TXD , P2.1-> UCA0RXD
+P2SEL0 &= ~(BIT0 | BIT1);
+P2SEL1 |= (BIT0 | BIT1);
+  * Set the baud rate.
+==== Baud Rate Configuration ====
+{{ :microcontrollers:uart2.png?direct&400 |}}
+Clock source 8 MHz and desired baud rate is 9600.
+Step1: N = 8000000/9600 > 16
+Step3: UCBRx = int (N/16) = 52 , OS16 = 1,
+UCBRFx = int( ( (N/16) – INT(N/16) ) × 16) =  1
+Step4: UCBRSx = 0x49 (by looking up the fractional part of N ( = N - INT(N) = 0.333333)
 ===== I2C (Inter-Integrated Circuit) =====
+The I2C lives on **UCBO** on a MSP430 board.
+{{ :microcontrollers:i2c.png?direct&400 |}}
+  * SDA: Data (default pin 1.6)
+  * SCL: Clock (default pin 1.7)
+Pull Low to send information.
+{{ :microcontrollers:i2c2.png?direct&400 |}}
+==== I2C Specifications ====
+  * Speed: 100 kbits/second - 3.4 Mbits/second
+  * Power: Bus draws power when SDA/SCL pulled low
+  * Vcc = 3.3V, Pullups = 4.7kΩ ∴ 0.7mA*2 = 1.4mA
+  * Larger resistors → Lower current draw
+  * Distance: I2C is limited by distance and the capacitance between SDA & SCL
+  * Designed for simple communication over a short distance
+==== Arbitration ====
+Using clock stretching, the bus can be easily arbitrated: this stalls the bus by holding SCL low.  This can be used to allow multiple nodes to be aware of when the bus is in use, or allow a device to stall the bus if more time is needed to handle data.
+==== Setup ====
+{{ :microcontrollers:i2c3.png?direct&400 |}}
+  * UCSWRST: Put USCI_B in reset state
+  * UCMODE_3: I2C Mode
+  * UCMST: Master Mode
+  * UCSYNC: Syncronous mode
+  * UCB0BRW: Baud rate SMCLK / 0x<UCB0BRW>
+==== Sending data ====
+{{ :microcontrollers:i2c4.png?direct&400 |}}
+==== Reading data ====
+{{ :microcontrollers:i2c5.png?direct&400 |}}
+{{ :microcontrollers:i2c6.png?direct&400 |}}
+===== References and Further Reading =====
+  * http://www.argenox.com/library/msp430/
+  * http://www.simplyembedded.org/tutorials/
+  * Msp430FR5994 User’s guide http://www.ti.com/lit/ug/slau367o/slau367o.pdf
+  * Evaluation of Power Efficiency for Digital Serial Interfaces of Microcontrollers  https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6208716