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by jpham
Fri Oct 05, 2018 10:49 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: run / global_en ?
Replies: 7
Views: 921

Re: run / global_en ?

thanks - I was confuse - usually the /reset means entire system reset (restart to a boot up state) the big question now - if I have a switch on my board, does the customer has to solder a wire from RPI board to my board? and why doesnt RSPI just put the "run" on a pin header? :-) - maybe they run ou...
by jpham
Fri Oct 05, 2018 2:01 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: run / global_en ?
Replies: 7
Views: 921

Re: run / global_en ?

ok, I'm confuse - two reply - shorting the pin to gnd - make the Pi wake up, the other - short to gnd -reset ?
can we get some clarification on how to do a system reset ? I look at the schematic - no system reset ?
by jpham
Thu Oct 04, 2018 3:19 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: run / global_en ?
Replies: 7
Views: 921

run / global_en ?

I notice the Run/global_en in RSPI 3B but not in RSPI 3B+ board - is it possible to send a RESET low from host computer to the RSPI RUN port?
assuming I convert my /RESET from 5V to 3.3V and solder my system /reset line to Raspberry RUN line ?
by jpham
Fri Sep 28, 2018 8:32 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Mechanica stuff - leg standoff length and screw
Replies: 7
Views: 770

Re: Mechanica stuff - leg standoff length and screw

well, it is the manufacturing in US since the 20s that set the standard in measurement for equipment - what's wrong with mils ? :-)

RAF - one of the world largest manufacturer of standoffs
Division of MW Industries, Inc.,
by jpham
Fri Sep 28, 2018 2:33 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Mechanica stuff - leg standoff length and screw
Replies: 7
Views: 770

Re: Mechanica stuff - leg standoff length and screw

All the big vendor like RAF list their hardware (standoffs etc) in inches - I go for mils - easier than inches
by jpham
Thu Sep 27, 2018 9:46 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Mechanica stuff - leg standoff length and screw
Replies: 7
Views: 770

Mechanica stuff - leg standoff length and screw

This is about mechanical size and stuff I'm looking for legs size (ie length and screw hole standard) for hat/pcb that lay on top of the Raspberry Pi 3/3+ with my board, I measured it to be 480 mils or 0.48" - The screw size seems to be 112 mils (?) the one next to the GPIO is so close to the gpio b...
by jpham
Wed Sep 26, 2018 5:15 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: how to use the GPIOs
Replies: 19
Views: 1894

Re: how to use the GPIOs

How about publish a document on how to use GPIO with common device like a UART - a 16550 Uart - simple 8bit bus, with /CS, /REset, /ioread and /iowrite - alot of common interface chip has that common features I like seeing those GPIO connect to blinking lights, but why buy a 1.2Ghz SBC module to do ...
by jpham
Sun Sep 23, 2018 8:16 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: mcp23x17 VDD voltage recomendation?
Replies: 1
Views: 550

mcp23x17 VDD voltage recomendation?

Since the Mcp23x17 VDD can be anywhere from 1.8v to 5.5V - what is the recommend voltage feeding the device?
How about other controller that can handle 3.3V, is there a recommendation on voltage - assuming I can put a 3.3V voltage
regulator on my hardware.
by jpham
Sun Sep 23, 2018 6:55 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: GPIO Bus termination?
Replies: 0
Views: 437

GPIO Bus termination?

I have a small bus - 4 pins sharing over 4 RSPI node - length - about 24 inches long
I'm using GPIO and not I2C or UART or spi or ethernet - just 3.3V GPIO from each module.
Do I need termination of each end of the net ?
by jpham
Sun Sep 23, 2018 8:35 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: extending the SPI /CS ?
Replies: 3
Views: 476

Re: extending the SPI /CS ?

I was planning to use the I2C, but after re-look at the min speed of I2C, it is just too slow - I2C max clock is like 1.7Mhz? I need to talk to the MCP23017 - and need the gpio to detect a 2Mhz clock ( need to set certain pin to low on a clock low) and a 1.7mhz clock serial is just too slow for that...
by jpham
Sat Sep 22, 2018 9:51 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: how to use the GPIOs
Replies: 19
Views: 1894

Re: how to use the GPIOs

instead of using RSP GPIO, I would recomend looking at Microchip MCP23017 (I2c) or MCP23S17 (SPI)
this gives you 16 GPIO per chip- if you use I2c, you can put it on the I2C Bus for a max of 8 device (x16 = 128 GPIO ports!!!)
enough for a blinking led show or some fancy I/O
by jpham
Sat Sep 22, 2018 9:38 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: extending the SPI /CS ?
Replies: 3
Views: 476

extending the SPI /CS ?

is it possible to use a 74HCT138 to decode the current two SPI /cs line so one can get 4 /CS ? or the current gpio scheme
we can't do that ? or should I use another 3 GPIO to send to the 138 decoder so I can get access to 8 SPI device?
by jpham
Sat Sep 22, 2018 9:35 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: wifi socket to multiple RSP?
Replies: 3
Views: 445

Re: wifi socket to multiple RSP?

I was also thinking of adding some resistor into the wifi line....like a 50 or 75ohms - there is no rule that say you can't do it

adding a hub would cost extra $$ - I'm thinking of the lowest cost network :-)
by jpham
Sat Sep 22, 2018 8:47 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: wifi socket to multiple RSP?
Replies: 3
Views: 445

wifi socket to multiple RSP?

I'm thinking of connecting multiple RSP over WIFI - but not over the air using antennas. What I'm proposing is connecting these RSP wifi antennas socket to a board that has the wifi socket so 8 or 10 RSPI doesn't need to transmit over the air - but via a copper lan/hub - of course there will be a WI...
by jpham
Sat Sep 22, 2018 6:15 pm
Forum: General programming discussion
Topic: GPIO programming
Replies: 1
Views: 3262

GPIO programming

GPIO programming - I have a group of GPIO ports (say port 10,11,12,13,14,15,16,17) as an 8bit data port - I want to set an 8bit data to that 8bit data port? is there a function to set that value or do i have to convert to binary and set each bit to each gpio individually? - how about 16 data port wi...
by jpham
Fri Sep 21, 2018 4:42 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Multiple RPI on I2C bus and hat EPROM
Replies: 5
Views: 938

Re: Multiple RPI on I2C bus and hat EPROM

right now just a test - I want the master to broadcast a sync every 10 sec
and the slave i2c would read that and sync

why did rasp put a pull up resistor on those two pins, wouldn't it better to put on the i2c bus
since the i2c resistance need to be calc and use certain resistor ?
by jpham
Thu Sep 20, 2018 5:55 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Multiple RPI on I2C bus and hat EPROM
Replies: 5
Views: 938

Re: Multiple RPI on I2C bus and hat EPROM

so if I have multiple RPI module, how do I set a module to be a slave on I2c bus? I use a couple GPIO pins as a hard wire node number
how do I tell the OS that this is I2C slave and node number - I like to use the node number as an I2c address

thanks
by jpham
Thu Sep 20, 2018 4:25 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Multiple RPI on I2C bus and hat EPROM
Replies: 5
Views: 938

Multiple RPI on I2C bus and hat EPROM

does the current code support multiple RPIs sharing the I2C bus and using one I2C configuration ROM?

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