drivers/video/max7456.c: Support for the Maxim MAX7456 on-screen-display chip.
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Bill Gatliff
Gregory Nutt
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5 changed files with 1739 additions and 0 deletions
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@ -22,6 +22,14 @@ config FB_OVERLAY_BLIT
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depends on FB_OVERLAY
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default n
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config VIDEO_MAX7456
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bool "Maxim 7456 Monochrome OSD"
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default n
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select SPI
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---help---
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Support for the Maxim 7456 monochrome on-screen display
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multiplexer.
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config VIDEO_OV2640
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bool "OV2640 camera chip"
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default n
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@ -51,6 +51,16 @@ endif
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endif
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# These video drivers depend on SPI support
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ifeq ($(CONFIG_SPI),y)
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ifeq ($(CONFIG_VIDEO_MAX7456),y)
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CSRCS += max7456.c
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endif
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endif
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# Include video driver build support
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DEPPATH += --dep-path video
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65
drivers/video/README.max7456
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65
drivers/video/README.max7456
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@ -0,0 +1,65 @@
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drivers/video/README.max7456
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23 March 2019
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Bill Gatliff <bgat@billgatliff.com>
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The code in max7456.[ch] is a preliminary device driver for the MAX7456 analog
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on-screen-display generator. This SPI slave chip is a popular feature in many
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embedded devices due its low cost and power requirements. In particular, you
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see it a lot on drone flight-management units.
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I use the term "preliminary" because at present, only the most rudimentary
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capabilities of the chip are supported:
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* chip reset and startup
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* read and write low-level chip control registers (DEBUG mode only)
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* write CA (Character Address) data to the chip's framebuffer memory
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Some key missing features are, in no particular order:
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* VSYNC and HSYNC synchronization (prevents flicker)
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* ability to update NVM (define custom character sets)
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If you have a factory-fresh chip, then the datasheet shows you what the factory
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character data set looks like. If you've used the chip in other scenarios,
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i.e. with Betaflight or similar, then your chip will almost certainly have had
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the factory character data replaced with something application-specific.
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Either way, you'll probably want to update your character set before long. I
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should probably get that working, unless you want to take a look at it
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yoruself...
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The max7456_register() function starts things rolling. The omnibusf4 target
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device provides an example (there may be others by the time you read this).
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In normal use, the driver creates a set of interfaces under /dev, i.e.:
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/dev/osd0/fb
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/dev/osd0/raw (*)
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/dev/osd0/vsync (*)
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* - not yet implemented
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By writing character data to the "fb" interface, you'll see data appear on the
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display. NOTE that the data you write is NOT, for example, ASCII text: it is
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the addresses of the characters in the chip's onboard character map.
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For example, if entry 42 in your onboard character map is a bitmap that looks
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like "H", then when you write the ASCII "*" (decimal 42, hex 2a), you'll see
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that "H" appear on your screen.
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If you build the code with the DEBUG macro defined, you will see a bunch more interfaces:
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/dev/osd0/VM0
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/dev/osd0/VM1
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/dev/osd/DMM
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...
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...
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These are interfaces to the low-level chip registers, which can be read and/or
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written to help you figure out what's going on inside the chip. They're
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probably more useful for me than you, but there they are in case I'm wrong
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about that.
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b.g.
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1575
drivers/video/max7456.c
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1575
drivers/video/max7456.c
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File diff suppressed because it is too large
Load diff
81
include/nuttx/video/max7456.h
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81
include/nuttx/video/max7456.h
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@ -0,0 +1,81 @@
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/****************************************************************************
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* include/nuttx/video/max7456.h
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*
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* Support for the Maxim MAX7456 Single-Channel Monochrome On-Screen
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* Display with Integrated EEPROM (datasheet 19-0576; Rev 1; 8/08).
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*
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* Copyright (C) 2019 Bill Gatliff. All rights reserved.
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* Author: Bill Gatliff <bgat@billgatliff.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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*****************************************************************************/
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#ifndef __INCLUDE_NUTTX_VIDEO_MAX7456_H
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#define __INCLUDE_NUTTX_VIDEO_MAX7456_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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/****************************************************************************
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* Public Data
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****************************************************************************/
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struct spi_dev_s;
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struct mx7_config_s
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{
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int spi_devid;
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FAR struct spi_dev_s *spi;
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};
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Name: max7456_register
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*
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* Description:
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* Registers an max7456 chip, and creates an interface 'devpath'
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*
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* Input Parameters:
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* path - The full path to the interface to register. E.g., "/dev/osd0"
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* config - Configuration information
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*
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* Returned Value:
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* Zero (OK) on success; a negated errno value on failure.
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*
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****************************************************************************/
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int max7456_register(FAR const char *path, FAR struct mx7_config_s *config);
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#endif /*__INCLUDE_NUTTX_VIDEO_MAX7456_H */
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