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Results tagged with spi
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user 35530
SPI is a low-level 3 or 4 wire serial bus interface with clock (SCLK), data in (MISO) and data out (MOSI). The fourth wire is a Slave Select to uniquely select a device on the bus. This signal is usually active-low. Slave Select, Chip Select, CS#, SS# stand for the same function, typically. Be sure to check the datasheet, though. The SPI bus is a *de facto* standard lacking the formal specification.
2
votes
Is using SPI communication for 3 meters length still tolerable?
I would expect problems if you try to use SPI directly- clock reflections as well as when you try to operate at higher speeds. … You can use SPI with a minor modification though- insert some LVDS drivers and receivers and drive balanced twisted-pair lines differentially in each direction. …
1
vote
SPI SS polarity
SPI-- there are four possibilities of clock polarity and phase, all of which have been used at one time or another.
There is no real standard in one place, just a defacto standard. … Usually the Motorola 68HC11 datasheets are pointed to for the origins of SPI. …
2
votes
SPI using one wire
Consider using IRDA rather than inventing a non-standard protocol. There are a number of speeds possible in IRDA: : SIR (115kbps), MIR (1Mbps), FIR (4Mbps), and VFIR (16Mbps)- with others up to 10G in …
6
votes
SPI max distance
You could use LVDS drivers and receivers to convert the single-ended logic signals into differential signals. Most reliable for a single drop setup (from the board to the external board only), and it …
1
vote
Resistors on SPI
Here is an example of a simple signal conditioning circuit that gives a nonlinear count-to-resistance equation. C1 should be a low leakage film type.
simulate this circuit – Schematic created …
2
votes
why is a crystal needed to program microcontrollers
It depends on the programming hardware the designers built into the chip.
Usually they want to be to program it (in some mode) without external components so they can be supplied pre-programmed.
B …
2
votes
MAX31855 and Type K sensor seem to top down at -60°C (should be measuring -80°C)
The MAX31855 applies no linearization, the equation:
VOUT = (41.276µV/°C) x (TR - TAMB)
is used.
Thermocouples such as K are more-or-less linear so it's good enough for narrow ranges near where t …
1
vote
Problem with SPI communication (PIC24H)
One of the errata on that chip is:
SPI Module The SPI transmit buffer full (SPITBF) flag does not get set immediately after writing to the buffer. …
0
votes
Accepted
Drive logic signals when power might be off
You could use a buffer such as a NC7SZ126- they have high output and input impedance even when powered down.
You might still want to include resistors if the two units are not close to each other an …
2
votes
Accepted
Why does the MCP4241 digital rheostat still work after Vdd is disconnected?
There are ESD protection networks on each input or output pin that act as diodes to Vcc and Vss. So it's completely possible for a CMOS chip to be powered inadvertently by an input (or, in this case, …
2
votes
Accepted
Computing Rise Time on SPI Bus
Yes, the rise time will be dominated by the current available from the GPIO pin (it's wrong to think of it as a resistance) and the capacitance. The trace resistance can be ignored.
Look at the guar …
4
votes
Accepted
ADC speed for precision medical instrument
SPI will almost surely give you a higher raw data rate than I2C (perhaps tens of MHz vs. perhaps 400kHz depending on the I2C flavor) but that may not be limiting for the LED switching rate. …
3
votes
Accepted
Using SPI to get higher sampling rate from ADC module vs using ADC on microcontroller
You could use an "Arduino" compatible module such as the STM32F103C8T6-based ones, which have claimed "12-bit" and "1us" ADC peripherals. Read the datasheet with a jaundiced eye to determine the actua …
2
votes
Accepted
SPI communication over different voltage
My preference is to use commercial voltage translators (the kind with two supplies and a direction pin) if you can't operate everything from 3.3V (the preferable solution) because SPI generally calls for …
1
vote
Accepted
SPI and word length
The closest thing to a standard that defines SPI is this (formerly Motorola) document.
There's no inherent limit in SPI as to word length. …