Difference between revisions of "Pico-sdk studies"

Revision as of 22:29, 18 August 2022

2022-08-15 Pico SDK Studies

ted@localhost:~/reference/pico-sdk$ grep -nr unreset_block_wait ./*
./src/rp2_common/hardware_resets/include/hardware/resets.h:88:static inline void unreset_block_wait(uint32_t bits) {
./src/rp2_common/hardware_uart/uart.c:34:    unreset_block_wait(uart_get_index(uart) ? RESETS_RESET_UART1_BITS : RESETS_RESET_UART0_BITS);
./src/rp2_common/pico_runtime/runtime.c:80:    unreset_block_wait(RESETS_RESET_BITS & ~(
./src/rp2_common/pico_runtime/runtime.c:110:    unreset_block_wait(RESETS_RESET_BITS);
./src/rp2_common/hardware_pll/pll.c:54:    unreset_block_wait(pll_reset);
./src/rp2_common/hardware_i2c/i2c.c:25:    unreset_block_wait(i2c == i2c0 ? RESETS_RESET_I2C0_BITS : RESETS_RESET_I2C1_BITS);
Binary file ./src/rp2_common/hardware_spi/.spi.c.swp matches
./src/rp2_common/hardware_spi/spi.c:18:    unreset_block_wait(spi == spi0 ? RESETS_RESET_SPI0_BITS : RESETS_RESET_SPI1_BITS);
./src/rp2_common/hardware_rtc/rtc.c:29:    unreset_block_wait(RESETS_RESET_RTC_BITS);
./src/rp2_common/hardware_adc/adc.c:14:    unreset_block_wait(RESETS_RESET_ADC_BITS);
./test/hardware_pwm_test/hardware_pwm_test.c:36:    unreset_block_wait(RESETS_RESET_PWM_BITS);

ted@localhost:~/reference/pico-sdk$

^ DMA driver details

2022-08-18

This section holds notes on RPi Pico SDK driver code for the RP2040 direct memory access unit. Goal here is to understand how Pico SDK structures its Application Programmers' Interface or API. We need to understand this in order to connect a Zephyr based application to code running on RP2040 and using its DMA. Likely we will need DMA when we enable and implement one or more SPI based peripherals, as SPI transmit and receive lines are often associated with a DMA controller to support high data transmission rates.

Search for . . .

ted@localhost:~/projects/zephyr-based/workspace-rpi-pico-work/pico-sdk$ grep -nr NUM_DMA_CHANNELS ./*
./src/host/pico_platform/include/hardware/platform_defs.h:12:#define NUM_DMA_CHANNELS 12u
. . .
./src/rp2040/hardware_structs/include/hardware/structs/dma.h:106:    dma_channel_hw_t ch[NUM_DMA_CHANNELS]; // 12
./src/rp2040/hardware_structs/include/hardware/structs/dma.h:194:    } ch[NUM_DMA_CHANNELS];

^ Pico assert.h definitions

RPi Pico SDK assert() definition is included in a section of this nn wiki page, as this Pico header file is included by both RPi Pico DMA driver and RPi Pico SPI driver. It is likely included by other Pico drivers and modules. We also include mention of this definition as recent studies of Zephyr third party drivers reveal that various projects each provide their own definitions of the C assert() construct.

$ find . -name assert.h
./common/pico_base/include/pico/assert.h

The contents of Pico SDK assert.h file are:

/*
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

// ---------------------------------------
// THIS FILE IS AUTOGENERATED; DO NOT EDIT
// ---------------------------------------

#ifndef _PICO_VERSION_H
#define _PICO_VERSION_H

#define PICO_SDK_VERSION_MAJOR    ${PICO_SDK_VERSION_MAJOR}
#define PICO_SDK_VERSION_MINOR    ${PICO_SDK_VERSION_MINOR}
#define PICO_SDK_VERSION_REVISION ${PICO_SDK_VERSION_REVISION}
#define PICO_SDK_VERSION_STRING   "${PICO_SDK_VERSION_STRING}"

#endif

^ Reference

• pico-sdk/src/rp2_common/README.md . . . document explains convention of Pico library routines which names of form hardware_ and pico_.