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boards/msb-430: Fix periph config & improve doc #19922

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Sep 14, 2023
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boards/msb-430: Fix periph config & improve doc #19922

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4 changes: 4 additions & 0 deletions boards/msb-430/Kconfig
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Expand Up @@ -20,4 +20,8 @@ config BOARD_MSB_430

select HAVE_SHT11

config ERROR_MODULES_CONFLICT
default "The msb-430 uses the same USART for UART and SPI" if MODULE_PERIPH_SPI && MODULE_PERIPH_UART
depends on BOARD_MSB_430

source "$(RIOTBOARD)/common/msb-430/Kconfig"
3 changes: 3 additions & 0 deletions boards/msb-430/Makefile.features
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Expand Up @@ -4,6 +4,9 @@ FEATURES_PROVIDED += periph_spi
FEATURES_PROVIDED += periph_timer
FEATURES_PROVIDED += periph_uart

FEATURES_CONFLICT += periph_spi:periph_uart
FEATURES_CONFLICT_MSG += "Both SPI and UART are provided by the same USART peripheral"

# Various other features (if any)

include $(RIOTBOARD)/common/msb-430/Makefile.features
41 changes: 38 additions & 3 deletions boards/msb-430/doc.txt
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Expand Up @@ -18,9 +18,9 @@
| FPU | no |
| Timers | 2 (2x 16bit) |
| ADCs | 1x 8 channel 12-bit |
| UARTs | 2 |
| SPIs | 2 |
| I2Cs | 1 |
| UARTs | 2 (*) |
| SPIs | 2 (*) |
| I2Cs | 1 (*) |
| Vcc | 1.8 V - 3.6 V (battery holder board provides 3.0 V) |
| Datasheet MCU | [Datasheet](https://www.ti.com/lit/ds/symlink/msp430f1612.pdf)|
| User Guide MCU | [User Guide](https://www.ti.com/lit/ug/slau049f/slau049f.pdf) |
Expand All @@ -32,13 +32,48 @@
is used, the supply voltage must initially be at least 2.0 V due to
the hysteresis of the SVS circuitry. Afterwards the MCU remains
operational with VCC >= 1.8 V.
@warning The MSP430F1612 has two USARTS, which can be configured as UART,
SPI, or (only in case of USART0) as I2C bus. Each USART can only
provide one serial interface at a time; time sharing is
theoretically possible but not yet implemented.

## Schematics

<img src="https://www.mi.fu-berlin.de/inf/groups/ag-tech/projects/ScatterWeb/pic/blueprints/MSB430_s1.png" alt="Schematics of the MSB-430 (Part 1 / 2)" style="width: 978px; max-width: 100%;">

<img src="https://www.mi.fu-berlin.de/inf/groups/ag-tech/projects/ScatterWeb/pic/blueprints/MSB430_s2.png" alt="Schematics of the MSB-430 (Part 2 / 2)" style="width: 1368px; max-width: 100%;">

### Hardware Limitations

The GPIOs on the MSP430F1612 only have two MUX settings: Being used as digital
input/output or routed to a peripheral. The MCU has two universal serial
synchronous/asynchronous communication interfaces (USARTs), which can be
used to provide either an UART, an SPI, or (only in case of USART0) an I2C bus.
Every USART signal is available at exactly one GPIO pin.

The UART exposed via the battery holder board (P3.6 and P3.7) can only be
provided via USART1. In order to support asynchronous reception (e.g. to allow
interaction via the shell), USART1 needs to be continuously configured as UART
and cannot be used to provide an SPI bus.

The SPI bus connected to the SD card socket (P5.1, P5.2, and P5.3) can only
be provided via USART1. Hence, it is not possible to use SPI bus connected to
the SD card socket while the UART used for `stdio` is in use, as they use the
same USART. They could be used at the same time, if module `stdin` is not used
(the UART is output only). However, sharing USARTs is not yet implemented.

The SPI bus of the CC1020 transceiver (used for configuration only) is connected
to pins P2.0, P2.1, and P2.3. Those pins are not connected to either USART, so
no hardware SPI can be used to interact with the transceiver. However, the SPI
is only used for configuration and control of the transceiver, so using a slow
bit-banging SPI bus won't affect the performance of the transceiver, other than
for quick power down after transmission or channel hopping. A second two
wire serial interface (not I2C or compatible) is used to feed data into
the CC1020 or read data from the CC1020. The serial clock is driven by the
transceiver and the MCU needs to keep up with providing the frames to send
bit by bit. Unlike modern transceivers, the CC1020 has no frame buffer and the
MCU needs to control the transmission and reception on the bit level.

## Pinout

### Pinout of the Main MSB 430 Board
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4 changes: 2 additions & 2 deletions boards/msb-430/include/periph_conf.h
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Expand Up @@ -80,8 +80,8 @@ static const msp430_clock_params_t clock_params = {
#define SPI_NUMOF (1U)

/* SPI configuration */
#define SPI_BASE (&USART_0)
#define SPI_SFR (&USART_0_SFR)
#define SPI_BASE (&USART_1)
#define SPI_SFR (&USART_1_SFR)
#define SPI_IE_RX_BIT (1 << 6)
#define SPI_IE_TX_BIT (1 << 7)
#define SPI_ME_BIT (1 << 6)
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