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external memory for data storage

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x3.exe

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Hi all,

I need to connect some external memory to the PIC in order to store data from ADC.
I am completely new to it, so I wanted to clarify a couple of things:

1. What type of memory would be suitable for this purpouse?
2.How can it be connected to uC and addressed?
3.How much slower will the uC access the external memory, comparing to its internal memory?
 

hi,

It all really depends on how much data you want to store - so if you are using a 10bit - 2byte adc result its that times the number of results you want to store.

Sd cards sound easy but have yet to find a simple proven circuit and software to do that.

EEprom is probably the next best choice if those chips are big enough for your needs ? - you can use several together.
They are connected by either the SPI or I2c bus, which Microchip have tutorials on if you are using assembler - I found the SPI easier to code.

Which ever type use go for be aware that some are 5v , some are 3v3, so its better to get one capable of running at your micros voltage rather than using a voltage level converter
 

I need to store data coming from an ADC which samples 4 channels at 8Khz frequency for up to 4 minutes, (each sample-2bytes). So I need a couple of megs of memory I guess. Which one of them is easier to interface to PIC ?
 

what about a serial flash?

Nandhu
 

wp100 said:
Sd cards sound easy but have yet to find a simple proven circuit ...
Click to expand...
SD cards work on +3.3V supply. If the PIC also runs on +3.3V, then the circuit is just SPI with pull-ups.

wp100 said:
...and software to do that.
Click to expand...
SD card file system for CCS compiler - https://www.smallridge.com.au/#SDFS. Worked from the 1st time for me. Be sure to check ROM and RAM requirements though.

x3.exe said:
data coming from an ADC which samples 4 channels at 8Khz frequency for up to 4 minutes, (each sample-2bytes).
Click to expand...
This is a very fast sampling rate for a PIC. Are you going to use PIC's ADC or external one(s)? If external, could you post the part number? Have you tested your data acquisition system at that rate?
 

I am using PIC33fj128gp802, which can sample 4 channels simultaneously using a built in ADC. I have tested the ADC module, it works fine. Now I want to transmit the data from adc to my laptop using UART, and that doesn't work very well, there is a timing issue that I haven't solved yet. The signal I get is shown in the attachment.
Are there any connectors or adaptors for interfacing SD card to microcontroller? you can't just solder the card directly to the PIC pins. [/img]
 

Assuming that I will buy **broken link removed** connector, how do I read data from specific address location. I have no experience with SPI at all, is it complicated to write the code for write and read functions? And what is the minimum memory block I can read from SD card?
 

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