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by EduardH
Thu May 13, 2021 11:48 am
Forum: General
Topic: Pico as I2C slave (solved)
Replies: 24
Views: 3130

Re: Pico as I2C slave (solved)

Hello, I spent a lot of time finding out why the Rpi master / I2c slave didn't work. The controller is an Rpi4B, the periferal the Pico. I folowed the main lines of the demo made by Penguintutor. Writing to the periferal, works fine. After a read the bus hangs. At first glance, my Rpi program was su...
by EduardH
Tue May 11, 2021 7:28 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C on Rpi4 in C language
Replies: 4
Views: 293

Re: I2C on Rpi4 in C language

Good evening, It took a lot of time figuring out why the Rpi4 master could write to the slave but not read. The slave is a raspberry pico. After all I changed the pico for an ordinary i2c integrated circuit. (a Philips TEA5767). From then on the bus was up and living. There must be something wrong i...
by EduardH
Sun May 09, 2021 7:58 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: I2C on Rpi4 in C language
Replies: 4
Views: 293

I2C on Rpi4 in C language

Good morning, I am looking for some code examples about using the I2C interface on a Rpi4 (or Rpi3B+). There are many examples wtih Python but I didn't find any in simple C language. The ultimate goal is connecting a pico to the Rpi4. The code on the pico seems to be working. The pico shows up in i2...
by EduardH
Sat Apr 18, 2020 6:17 pm
Forum: General discussion
Topic: getting a pixel
Replies: 9
Views: 854

Re: getting a pixel

Hello Heater, We better call it a Mihaly tv. Dénes Mihaly was an Hungarian inventor who founded the Telehor company. This disk is a Telehor model. In the year 1884 Nipkow has invented the scanning disk. It took many years before radio was at a technical level for being able to transmit pictures. Man...
by EduardH
Sat Apr 18, 2020 3:14 pm
Forum: General discussion
Topic: getting a pixel
Replies: 9
Views: 854

Re: getting a pixel

Hello Heater, Please find a photo of the disk. foto4.jpg On the right there is a Mojo FPGA board with a low pass filter to get the video signal. (the same way the Rpi outputs sound) The circuits are powered buy a laptop power supply. Even a small movie seems too big for an attachment. Please find on...
by EduardH
Sat Apr 18, 2020 10:23 am
Forum: General discussion
Topic: getting a pixel
Replies: 9
Views: 854

Re: getting a pixel

Good afternoon, Thanks for the answers. You gave me a number of starting points to go on. I want to answer Your questions. For the moment the pi is not connected to the Nipkow disk. I added an optical detector to the turning disk. The disk has 30 holes to make a 30 line picture as described in the G...
by EduardH
Fri Apr 17, 2020 11:50 am
Forum: General discussion
Topic: getting a pixel
Replies: 9
Views: 854

getting a pixel

Dear forum, I built some electronics around a Nipkow disk, a 90 years old mechanical television. The disk is now presenting test pictures consisting 30 rows and 64 columns. I wonder if there exists, in the Raspbian OS, some C function that allows me to read the red/green/blue values of each pixel sh...
by EduardH
Thu Oct 31, 2019 9:19 pm
Forum: Bare metal, Assembly language
Topic: Rpi4, pin7, GPIO4 clock output
Replies: 3
Views: 1292

Re: Rpi4, pin7, GPIO4 clock output

Thank You Joan, To my opinion its a bit a bare metal question. It is low level. GPIO4 is directly programmed from the hardware registers. Meanwhile I found an easy method to handle the different Rpi models. I ordered a 50 MHz MEMS oscillator. Size 3x2 mm for less then 3 euros. There is plenty of roo...
by EduardH
Thu Oct 31, 2019 10:17 am
Forum: Bare metal, Assembly language
Topic: Rpi4, pin7, GPIO4 clock output
Replies: 3
Views: 1292

Rpi4, pin7, GPIO4 clock output

Hello, I used to divide the 500 MHz system clock to generate a 50 MHz clock on GPIO4. It works fine with the Rpi zero, Rpi2, Rpi3. I only had to change the peripheral base address after installing the code on an other model. For the Rpi3 it takes the value 0x3F00 0000. I found that the base address ...
by EduardH
Tue Jan 29, 2019 5:52 pm
Forum: General programming discussion
Topic: starting aplay from a C program
Replies: 3
Views: 1160

Re: starting aplay from a C program

Hello Jahboater, Indeed, it is a named pipe located on a ram disk. I used a fifo because the first in first out is a matter of fact. Maybe a file can be used but then I have to manage full and empty myself. As far as I know aplay plays the file to the end. If the end of file is reached aplay stops. ...
by EduardH
Tue Jan 29, 2019 3:49 pm
Forum: General programming discussion
Topic: starting aplay from a C program
Replies: 3
Views: 1160

starting aplay from a C program

Good afternoon. Strange things are happening. Please give me a hint if You know what is going on. I wrote a C program on a rpi zero WH. The program runs some code and the result is dumped in a fifo. The output of the fifo is read by the aplay utility. Two sound channels are output to the pwm pins on...
by EduardH
Thu Oct 11, 2018 9:20 am
Forum: General discussion
Topic: where to buy rpi zero 1.3 for builing a cluster
Replies: 19
Views: 2981

Re: where to buy rpi zero 1.3 for builing a cluster

Good moring, @jamesh: Thank You for all these information. It's not at all my intention to abuse charity to get low prices. No problem to pay a fair price. The project is still in the prototype status. At the moment it makes no sense to buy 500 pieces or more. You have well explained why the zero is...
by EduardH
Mon Oct 08, 2018 9:13 am
Forum: General discussion
Topic: where to buy rpi zero 1.3 for builing a cluster
Replies: 19
Views: 2981

Re: where to buy rpi zero 1.3 for builing a cluster

Good morning, Indeed, it is not that easy to buy several rpi zero 1.3 but I found distributors selling the 8086 pi hat as a kit with four rpi zero included. I'll look for that. @ejoison: The project I am working on is meant for museums and collectors who have a large collection of old tube radio's. ...
by EduardH
Sun Oct 07, 2018 9:45 am
Forum: General discussion
Topic: where to buy rpi zero 1.3 for builing a cluster
Replies: 19
Views: 2981

where to buy rpi zero 1.3 for builing a cluster

Good morning, I want to buy or build a cluster with rpi zero 1.3 boards. The rpi hat that joins 4 rpi zero + one rpi3 could be a nice solution to start. The problem is that my local distributors have restricted selling the rpi zero to one piece a client. Even multiple orders will be cancelled. This ...
by EduardH
Sat Feb 24, 2018 6:26 pm
Forum: Bare metal, Assembly language
Topic: what is wrong with this bare metal code.
Replies: 4
Views: 1637

Re: what is wrong with this bare metal code.

Many thanks for Your help. Indeed, I understand what I did wrong. I want to find out why my program (on Rpi0, rpi2 and rpi3) worked much slower then I expected and what can be done to give it a speed boost. It must be something like the cache or the prediction OFF. I just went from the "baking ...
by EduardH
Tue Feb 20, 2018 6:00 pm
Forum: Bare metal, Assembly language
Topic: what is wrong with this bare metal code.
Replies: 4
Views: 1637

Re: what is wrong with this bare metal code.

Hello LdB, Thanks for Your help. I posed a question and got answers to 3 questions. Indeed writing to CLR would not set the GPIO bit. That doesn't change much because a few lines later there is a write to SET in the loop. (not shown here) ldr r3,[r0, #0x28] loads the contents of location 2020 0028 i...
by EduardH
Tue Feb 20, 2018 2:07 pm
Forum: Bare metal, Assembly language
Topic: what is wrong with this bare metal code.
Replies: 4
Views: 1637

what is wrong with this bare metal code.

Good afternoon, I made a blinking led; OK02 from "baking pi". I modified the program for blinking GPIO0. In the code there is something like str r1,[r0, #0x28]. It works fine. Then I replaced this line by two others: ldr r3,[r0, #0x28] str r1, [r3] The second code snippet did not work. in ...
by EduardH
Sat Feb 10, 2018 9:45 am
Forum: Bare metal, Assembly language
Topic: GPIO4 and GPIO5
Replies: 1
Views: 1589

Re: [solved] GPIO4 and GPIO6 instead of GPIO5

Good morning, My question about generating two independently selectable frequencies is solved. Using GPIO5 for the second output was a bad idea. The system seems to use the signal behind GPIO5 for its own. There is one line telling that in this text: https://raspberrypi.stackexchange.com/questions/1...
by EduardH
Fri Feb 09, 2018 5:54 pm
Forum: Bare metal, Assembly language
Topic: GPIO4 and GPIO5
Replies: 1
Views: 1589

GPIO4 and GPIO5

Good evening, I want to use the rpi zero for generating two square waves. Speed between 500 kHz and 1700 kHz. No problem using GPIO4 (pin 7). With only a few lines bare metal assembler it works fine. I used the information from page 102 in the BCM2835 Peripheral manual. Why doesn’t the same method w...
by EduardH
Thu Jan 25, 2018 12:37 pm
Forum: Bare metal, Assembly language
Topic: rpi3 speed vs rpi zero
Replies: 2
Views: 967

Re: rpi3 speed vs rpi zero

Thank You LdB, First of all I want to says there is an error in my first message. Timing is not nanoseconds but microseconds. The rpi zero is now the winner having 75 ns per loop iteration. That is 25 ns / instruction. I repeated the experiment with an rpi2 with BCM2836. It's even worse than the rpi...
by EduardH
Thu Jan 25, 2018 11:05 am
Forum: Bare metal, Assembly language
Topic: rpi3 speed vs rpi zero
Replies: 2
Views: 967

rpi3 speed vs rpi zero

Good morning, I am beginning with bare metal on the raspberry. To make an easy start with the Cambridge tutorial I ordered the rpi Zero. No problem to program the blinking led from lesson OK02. After recompiling the exercise with another base address and renaming the output to "kernel7.img"...
by EduardH
Sun Oct 29, 2017 8:51 pm
Forum: Bare metal, Assembly language
Topic: How to start bare metal progamming
Replies: 4
Views: 2708

Re: How to start bare metal progamming

Thank You Dwelch67 and Traveller, I have got enough information to start. Indeed, why not buy the zero and start in C language. Soldering a dual row print header is no problem. I have a working knowledge in C programming. It's my favourite language on pic and 8051. Once started in C, I could switch ...
by EduardH
Sun Oct 29, 2017 9:23 am
Forum: Bare metal, Assembly language
Topic: How to start bare metal progamming
Replies: 4
Views: 2708

How to start bare metal progamming

Good morning, I want to start bare metal programming. I am familiar with 8051 and pic microprocessors. My linux kwowledgd is at “user” level. The internet lessons from Cambride university are made for the old rpi 1 model A of model B. There is a warning that the models A+ and B+ wont work. Neither m...
by EduardH
Sat Dec 03, 2016 1:14 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: SPI sound card
Replies: 1
Views: 1519

Re: SPI sound card

Hello, It seems nobody has ever made a simple spi soundcard. After many hours mine is working. Please find the rpi2 and the pic source code. The PIC 16F1718 is working well as a soundcard. Fore sure a 8 bit dac is no hifi. Next step will be the modulation on a medium wave carrier. This is not a rasp...
by EduardH
Fri Nov 18, 2016 11:15 am
Forum: Troubleshooting
Topic: Browser no livestream playback
Replies: 17
Views: 2980

Re: Browser no livestream playback

Hello everyone, Because I needed the rpi2 for other things I finally bought a rpi3. I am glad to tell You that browing to the local television with Chromium works much better. It seems that the higher rpi3 speed is just enough to give a nice picture with a sound that is nearly perfect. (only a few s...

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