From a7df8adc5c9b3aa3f1cf0a908a12a7ba6e8048bf Mon Sep 17 00:00:00 2001
From: Robert Harft <roberthart56@gmail.com>
Date: Sun, 15 Jan 2023 10:27:38 -0500
Subject: [PATCH] add material
---
README.md | 6 +++++
code/SPI_23K256/SPI_23K256.py | 41 ++++++++++++++++++++++++++++++-----
2 files changed, 41 insertions(+), 6 deletions(-)
diff --git a/README.md b/README.md
index bc91143..d2e11b8 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,12 @@ pulses cease and CS is deasserted."
##23K256 memory chip as an example of SPI
+The 23K256 is a 32KByte memory device with a limited set of commands and registers. Good exercise for doing SPI at a low-ish level, using the MicroPython machine functions and referring to eh chip's datasheet.
+
[Datasheet for 23K256:](https://ww1.microchip.com/downloads/en/DeviceDoc/22100F.pdf)
Set Polarity equal to zero for this chip. This is the level of the idle clock. See [SPI spec for MicroPython](https://docs.micropython.org/en/latest/library/machine.SPI.html)
+
+[Here is a code that works](./code/SPI_23K256/SPI_23K256.py) to store and retrieve numbers from the 23K256. All operations are written out. Next step would be to put them in functions and create a library file for this chip.
+
+This is a nice example of a simple but non-trivial protocol for SPI.
diff --git a/code/SPI_23K256/SPI_23K256.py b/code/SPI_23K256/SPI_23K256.py
index 7e31dfd..575b2ca 100644
--- a/code/SPI_23K256/SPI_23K256.py
+++ b/code/SPI_23K256/SPI_23K256.py
@@ -4,15 +4,23 @@ import time
###############################################################################
# Constants
+#commands
READ = 0x03
WRITE = 0x02
READ_S_R = 0x05
WRITE_S_R = 0x01
+# Bits to determine mode
SEQ_RW = 0x01 << 6 #B6 is 1
BYTE_RW = 0x00 << 6 #zeros
PAGE_RW = 0x02 << 6 #B7 is 1
+#address
+ADDR_HIGH = 0x00
+ADDR_LOW = 0x00
+
+#content
+value_stored = 255
########################################################
@@ -33,25 +41,46 @@ spi = machine.SPI(0,
miso=machine.Pin(4))
-#write to status register
+#write to status register to set mode.
cs.value(1)
msg = bytearray()
msg.append(WRITE_S_R)
-msg.append(SEQ_RW)
-print(msg)
+msg.append(BYTE_RW)
+#print(msg)
cs.value(0)
spi.write(msg)
cs.value(1)
-#read status register
+#read status register, to check mode.
msg = bytearray()
msg.append(READ_S_R)
-
cs.value(0)
spi.write(msg)
data = spi.read(1)
cs.value(1)
-print(data)
+print("mode=",data)
+
+#form address
+msg = bytearray([WRITE, ADDR_HIGH, ADDR_LOW])
+
+#form writing array
+val = bytearray([value_stored])
+print("number stored =",val)
+
+#Write to address
+cs.value(0)
+spi.write(msg)
+spi.write(val)
+cs.value(1)
+
+time.sleep(0.01)
+#Read from address
+msg = bytearray([READ, ADDR_HIGH, ADDR_LOW])
+cs.value(0)
+spi.write(msg) #same address
+data = spi.read(1)
+cs.value(1)
+print('number read = ',data)
\ No newline at end of file
--
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