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--- microcontrollers:common_communication_types [2024/10/30 18:59] – [SPI Modes- Phase (PH) and Polarity (POL) bits] ibchadmin
+++ microcontrollers:common_communication_types [2024/10/30 19:21] (current) – ibchadmin
@@ Line 19: / Line 19: @@
 A combination of  phase and polarity produces 4 standard modes for the clock in SPI:
-^ Mode  ^ CPOL/CKPL  | CPHA/CKPH  |
+^ Mode  ^ CPOL/CKPL  | **CPHA/CKPH**  |
-| 0     | 0          | 0          |
+| 0     | 0          | 0              |
-| 1     | 0          | 1          |
+| 1     | 0          | 1              |
-| 2     | 1          | 0          |
+| 2     | 1          | 0              |
-| 3     | 1          | 1          |
+| 3     | 1          | 1              |
 It is important that the right phase and polarity are selected so that the slave and master both capture the bit at the correct clock transition.
+==== SPI Communication ====
+  * Select the Universal Serial Communication Interface (USCI) modules (USCI_A and USCI _B) or the universal Serial Interface (USI). Some  devices have more than one USCI in which called USCI_A0, USCI_A1 and so on.
+  * Configure the  3 Pins (Clock, MOSI, SOMI) for SPI by configuring PxSEL0 and PxSEL1 to select the SPI function for those pins. (refer to the datasheet of your microcontroller to knew what value you should assign for each register).
+	Example using UCB0 module for MSp430Fr5969
+  P1SEL1 |= BIT6;  // P1.6-> UCB0SIMO
+  P1SEL1 |= BIT7 ; //P1.7-> UCB0SOMI
+  P2SEL1 |= BIT2 ; //P2.2-> UCB0CLK
+  * Set up the CS pin as output.
+  * Set up the Clock speed and mode that match the salve speed and mode. (refer to the slave’s datasheet)
 ===== UART (Universal Asynchronous Receiver-Transmitter) =====
+{{ :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