boards/atmega8: new board

boards/atmega8/Kconfig

@@ -0,0 +1,25 @@
+# Copyright (c) 2020 HAW Hamburg
+#
+# This file is subject to the terms and conditions of the GNU Lesser
+# General Public License v2.1. See the file LICENSE in the top level
+# directory for more details.
+
+config BOARD
+    default "atmega8" if BOARD_ATMEGA8
+
+config BOARD_ATMEGA8
+    bool
+    default y
+    select CPU_MODEL_ATMEGA8
+    # Put defined MCU peripherals here (in alphabetical order)
+    select HAS_PERIPH_ADC
+    select HAS_PERIPH_GPIO
+    select HAS_PERIPH_I2C
+    select HAS_PERIPH_PWM
+    select HAS_PERIPH_SPI
+    select HAS_PERIPH_TIMER
+    select HAS_PERIPH_UART
+    # Various other features (if any)
+    select MODULE_BOARDS_COMMON_ATMEGA if TEST_KCONFIG
+
+source "$(RIOTBOARD)/common/atmega/Kconfig"

boards/atmega8/Makefile

@@ -0,0 +1,5 @@
+MODULE = board
+
+DIRS = $(RIOTBOARD)/common/atmega
+
+include $(RIOTBASE)/Makefile.base

boards/atmega8/Makefile.dep

@@ -0,0 +1 @@
+USEMODULE += boards_common_atmega

boards/atmega8/Makefile.features

@@ -0,0 +1,9 @@
+CPU = atmega8
+
+FEATURES_PROVIDED += periph_adc
+FEATURES_PROVIDED += periph_gpio
+FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_pwm
+FEATURES_PROVIDED += periph_spi
+FEATURES_PROVIDED += periph_timer
+FEATURES_PROVIDED += periph_uart

boards/atmega8/Makefile.include

@@ -0,0 +1,16 @@
+# configure the terminal program
+PORT_LINUX          ?= /dev/ttyUSB0
+PORT_DARWIN         ?= $(firstword $(sort $(wildcard /dev/tty.usbmodem*)))
+BAUD                ?= 9600
+ATMEGA8_CLOCK    	?=
+
+# Allow overwriting programmer via env variables without affecting other boards
+PROGRAMMER_BOARD_ATMEGA8 ?= usbasp
+# ICSP programmer to use for avrdude
+AVRDUDE_PROGRAMMER ?= $(PROGRAMMER_BOARD_ATMEGA8)
+
+ifneq (,$(ATMEGA8_CLOCK))
+  CFLAGS += -DCLOCK_CORECLOCK=$(ATMEGA8_CLOCK)
+endif
+
+include $(RIOTBOARD)/common/atmega/Makefile.include

boards/atmega8/doc.txt

@@ -0,0 +1,99 @@
+/**
+@defgroup    boards_atmega8 Standalone ATmega8
+@ingroup     boards
+@brief       Support for using the ATmega8 as standalone board
+
+## Overview
+
+As the ATmega8 can run from the internal oscillator, placing it on a breadboard,
+connecting an USB-UART adapter and power is enough to run RIOT on it. (An ISP
+programmer will be needed to program it; or to program a bootloader to
+subsequently allow programming via UART.)
+
+### MCU
+| MCU           | ATmega8                                       |
+|:------------- |:--------------------------------------------- |
+| Family        | AVR/ATmega                                    |
+| Vendor        | Microchip (previously Atmel)                  |
+| RAM           | 1KiB                                          |
+| Flash         | 8KiB                                          |
+| EEPROM        | 512B                                          |
+| Frequency     | 1MHz/8MHz (up to 16MHz with external clock)   |
+| Timers        | 3 (2x 8bit, 1x 16bit)                         |
+| ADCs          | 6 analog input pins                           |
+| UARTs         | 1                                             |
+| SPIs          | 1                                             |
+| I2Cs          | 1 (called TWI)                                |
+| Vcc           | 4.5V - 5.5V (ATmega8), 2.7V - 5.5V (ATmega8L) |
+| Datasheet     | [Official datasheet](https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-2486-8-bit-AVR-microcontroller-ATmega8_L_datasheet.pdf) |
+
+### Pinout
+
+\htmlonly<style>div.image img[src="https://camo.githubusercontent.com/c55beef2f138da61fe671a1e4a307ff4ffbc318d/68747470733a2f2f692e696d6775722e636f6d2f715849456368542e6a7067"]{width:100%;}</style>\endhtmlonly
+@image html "https://camo.githubusercontent.com/c55beef2f138da61fe671a1e4a307ff4ffbc318d/68747470733a2f2f692e696d6775722e636f6d2f715849456368542e6a7067" "Pinout of the ATmega328p"<br>
+
+All credit for above pinout image goes to https://github.com/MCUdude/MiniCore#pinout
+
+### Clock Frequency
+
+The ATmega8 has an internal oscillators clocked at 1MHz that allow it to be
+operated without any external clock source or crystal. By default the fuses are
+configured to use the internal oscillator and an operating mode resulting in a
+clock speed of 1MHz. By setting the `CKSEL` fuses to 0100 the clock will operate
+at 8MHz without an external clock source. This can be done like this:
+
+    avrdude -c usbasp -p m8 -B 32 -U lfuse:w:0xe4:m
+
+(Replace `usbasp` with the ISP programmer you are using. The `-B 32` might
+be needed on some ISP programmers to communicate with slow ATmega MCUs. It will
+not be needed anymore after the clock device has been disabled.)
+
+This "board" is configured to use 8MHz as core clock, so that the ATmega8
+runs at the highest frequency possible without external clock sources.
+
+By setting the environment variable `ATMEGA8_CLOCK` to a custom frequency in
+Hz (e.g. `1000000` for 1MHz), this core clock can be changed easily. Refer to
+the datasheet on how to configure the ATmega8 to use an external crystal, an
+external clock source or the clock divider.
+
+### Relation Between Supply Voltage, Clock Frequency and Power Consumption
+
+A higher supply voltage results in a higher current drawn. Thus, lower power
+consumption can be achieved by using a lower supply voltage. However, higher
+clock frequencies require higher supply voltages for reliable operation.
+
+The lowest possible supply voltage at 8 MHz is 2.7V (Atmega8L) or
+4.5V (Atmega8).
+
+## Flashing the Device
+
+In order to flash the ATmega8 without a bootloader, an ISP programmer is
+needed. Connect the programmer as follows:
+
+| ISP pin  | ATmega8 pin    |
+|:-------- |:-------------- |
+| MISO     | 18/PB4/MISO    |
+| VCC      | 7/VCC          |
+| SCK      | 19/PB5/SCK     |
+| MOSI     | 17/PB3/MOSI    |
+| RESET    | 1/RESET        |
+| Ground   | 22/GND         |
+
+The tool `avrdude` needs to be installed. When using the `usbasp` running
+
+    make BOARD=atmega8 flash
+
+will take care of everything. To use the programmer `<FOOBAR>` instead, run
+
+    make BOARD=atmega8 PROGRAMMER=<FOOBAR> flash
+
+## Serial Terminal
+
+Connect a TTL adapter with pins 2/RXD and 3/TXD an run
+
+    make BOARD=atmega8 term
+
+Please note that the supply voltage should be compatible with the logic level of
+the TTL adapter. Usually everything between 3.3 V and 5 V should work.
+
+ */

boards/atmega8/include/board.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2014 Freie Universität Berlin, Hinnerk van Bruinehsen
+ *               2016 Laurent Navet <laurent.navet@gmail.com>
+ *               2019 Otto-von-Guericke-Universität Magdeburg
+ *               2023 Hugues Larrive
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     boards_atmega8
+ * @{
+ *
+ * @file
+ * @brief       Board specific definitions for the standalone ATmega8 "board"
+ *
+ * @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ * @author      Hinnerk van Bruinehsen <h.v.bruinehsen@fu-berlin.de>
+ * @author      Laurent Navet <laurent.navet@gmail.com>
+ * @author      Hugues Larrive <hugues.larrive@pm.me>
+ */
+
+#ifndef BOARD_H
+#define BOARD_H
+
+#include "cpu.h"
+#include "periph_conf.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name    STDIO configuration
+ *
+ * As the CPU is too slow to handle 115200 baud, we set the default
+ * baudrate to 9600 for this board
+ * @{
+ */
+#define STDIO_UART_BAUDRATE (9600U)
+/** @} */
+
+/**
+ * @name    xtimer configuration values
+ * @{
+ */
+#define XTIMER_WIDTH                (16)
+#if CLOCK_CORECLOCK > 4000000UL
+#define XTIMER_HZ                   (CLOCK_CORECLOCK / 64)
+#else
+#define XTIMER_HZ                   (CLOCK_CORECLOCK / 8)
+#endif
+#define XTIMER_BACKOFF              (40)
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BOARD_H */
+/** @} */

boards/atmega8/include/periph_conf.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2019 Otto-von-Guericke-Universität Magdeburg
+ *               2023 Hugues Larrive
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup boards_atmega8
+ * @{
+ *
+ * @file
+ * @brief   Peripheral MCU configuration for the ATmega8 standalone "board"
+ *
+ * @author  Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ * @author  Hugues Larrive <hugues.larrive@pm.me>
+ */
+
+#ifndef PERIPH_CONF_H
+#define PERIPH_CONF_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @name    Clock configuration
+ * @{
+ */
+#ifndef CLOCK_CORECLOCK
+/* Using 8MHz internal oscillator as default clock source */
+#define CLOCK_CORECLOCK     (8000000UL)
+#endif
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#include "periph_conf_atmega_common.h"
+
+#endif /* PERIPH_CONF_H */
+/** @} */

boards/common/atmega/include/periph_conf_atmega_common.h

@@ -6,6 +6,7 @@
  *               2017 HAW Hamburg, Dimitri Nahm
  *               2018 Matthew Blue <matthew.blue.neuro@gmail.com>
  *               2019 Otto-von-Guericke-Universität Magdeburg
+ *               2023 Hugues Larrive
  *
  * This file is subject to the terms and conditions of the GNU Lesser
  * General Public License v2.1. See the file LICENSE in the top level
@@ -28,6 +29,7 @@
  * @author      Matthew Blue <matthew.blue.neuro@gmail.com>
  * @author      Francisco Acosta <francisco.acosta@inria.fr>
  * @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ * @author      Hugues Larrive <hugues.larrive@pm.me>
  */
 
 #ifndef PERIPH_CONF_ATMEGA_COMMON_H
@@ -71,6 +73,12 @@ extern "C" {
     #define UART_1              MEGA_UART1
     #define UART_1_ISR          USART1_RX_vect
     #define UART_1_ISR_TX       USART1_TX_vect
+#elif defined(CPU_ATMEGA8)
+    #define UART_NUMOF          (1U)
+
+    #define UART_0              MEGA_UART
+    #define UART_0_ISR          USART_RXC_vect
+    #define UART_0_ISR_TX       USART_TXC_vect
 #elif defined(CPU_ATMEGA328P)
     #define UART_NUMOF          (1U)
 
@@ -156,7 +164,8 @@ extern "C" {
  */
 #ifndef ADC_NUMOF
 #if defined(CPU_ATMEGA128RFA1) || defined(CPU_ATMEGA256RFR2) || defined(CPU_ATMEGA328P) ||  \
-    defined(CPU_ATMEGA1281) || defined(CPU_ATMEGA1284P) || defined(CPU_ATMEGA32U4)
+    defined(CPU_ATMEGA1281) || defined(CPU_ATMEGA1284P) || defined(CPU_ATMEGA32U4) || \
+    defined(CPU_ATMEGA8)
     #define ADC_NUMOF           (8U)
 #elif defined (CPU_ATMEGA2560)
     #define ADC_NUMOF           (16U)
@@ -180,7 +189,9 @@ extern "C" {
  * @{
  */
 #ifndef PWM_NUMOF
-#if defined(CPU_ATMEGA328P)
+#if defined(CPU_ATMEGA8)
+    #define PWM_PINS_CH0 { GPIO_PIN(PORT_B, 3), GPIO_UNDEF }
+#elif defined(CPU_ATMEGA328P)
     #define PWM_PINS_CH0 { GPIO_PIN(PORT_D, 6), GPIO_PIN(PORT_D, 5) }
     #define PWM_PINS_CH1 { GPIO_PIN(PORT_B, 3), GPIO_PIN(PORT_D, 3) }
 #elif defined(CPU_ATMEGA1281)
@@ -200,8 +211,9 @@ extern "C" {
 
 #if defined(CPU_ATMEGA32U4) || defined(CPU_ATMEGA328P) || \
     defined(CPU_ATMEGA1281) || defined(CPU_ATMEGA1284P) || \
-    defined(CPU_ATMEGA2560)
+    defined(CPU_ATMEGA2560) || defined(CPU_ATMEGA8)
     static const pwm_conf_t pwm_conf[] = {
+#ifndef CPU_ATMEGA8
         {
             .dev = MINI_TIMER0,
             .pin_ch = PWM_PINS_CH0,
@@ -213,6 +225,13 @@ extern "C" {
             .pin_ch = PWM_PINS_CH1,
             .div = MINI_TIMER2_DIV,
         }
+#endif
+#else /* CPU_ATMEGA8 */
+        {
+            .dev = MINI_TIMER2,
+            .pin_ch = PWM_PINS_CH0,
+            .div = MINI_TIMER2_DIV,
+        },
 #endif
     };