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feat: support multi-byte reads for device registers #31

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Merged
merged 1 commit into from
Jul 29, 2024
Merged

feat: support multi-byte reads for device registers #31

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31 changes: 16 additions & 15 deletions feeph/i2c/burst_handler.py
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Original file line number Diff line number Diff line change
Expand Up @@ -62,17 +62,16 @@ def read_register(self, register: int, byte_count: int = 1, max_tries: int = 5)
- may raise a RuntimeError if there were too many errors
"""
_validate_inputs(register=register, value=0, byte_count=byte_count, max_tries=max_tries)
if byte_count > 1:
LH.warning("Multi byte reads are not implemented yet! Returning a single byte instead.")
byte_count = 1
for cur_try in range(1, 1 + max_tries):
try:
buf_r = bytearray(1)
buf_r = bytearray(byte_count)
buf_r[0] = register
buf_w = bytearray(byte_count)
self._i2c_bus.writeto_then_readfrom(address=self._i2c_adr, buffer_out=buf_r, buffer_in=buf_w)
# TODO properly handle multi byte reads
return buf_w[0]
value = 0
for i in range(byte_count):
value += buf_w[i] << i*8
return value
except OSError as e:
# [Errno 121] Remote I/O error
LH.warning("[%s] Failed to read register 0x%02X (%i/%i): %s", __name__, register, cur_try, max_tries, e)
Expand All @@ -91,15 +90,16 @@ def write_register(self, register: int, value: int, byte_count: int = 1, max_tri
- may raise a RuntimeError if there were too many errors
"""
_validate_inputs(register=register, value=value, byte_count=byte_count, max_tries=max_tries)
if byte_count > 1:
LH.warning("Multi byte writes are not implemented yet! Returning a single byte instead.")
byte_count = 1
for cur_try in range(1, 1 + max_tries):
try:
buf = bytearray(1 + byte_count)
buf = bytearray(1 + byte_count) # buf[0], buf[1], buf[2]
buf[0] = register
buf[1] = value & 0xFF
# TODO properly handle multi byte reads
# need to populate the bytes in reverse order:
# 0x##.. => buf[2]
# 0x..## => buf[1]
for i in range(byte_count, 0, -1):
buf[i] = value & 0xFF
value = value >> 8
self._i2c_bus.writeto(address=self._i2c_adr, buffer=buf)
return
except OSError as e:
Expand All @@ -112,6 +112,9 @@ def write_register(self, register: int, value: int, byte_count: int = 1, max_tri
else:
raise RuntimeError(f"Unable to read register 0x{register:02X} after {cur_try} attempts. Giving up.")

# it is unclear if it's possible to have a multi-byte state registers
# (a register write looks exactly like a multi-byte state write)

def get_state(self, byte_count: int = 1, max_tries: int = 5) -> int:
"""
get current state of I²C device identified by `i2c_adr` and
Expand All @@ -127,7 +130,6 @@ def get_state(self, byte_count: int = 1, max_tries: int = 5) -> int:
for cur_try in range(1, 1 + max_tries):
try:
buf = bytearray(byte_count)
# TODO properly handle multi byte reads
self._i2c_bus.readfrom_into(address=self._i2c_adr, buffer=buf)
return buf[0]
except OSError as e:
Expand Down Expand Up @@ -155,7 +157,6 @@ def set_state(self, value: int, byte_count: int = 1, max_tries: int = 3):
try:
buf = bytearray(byte_count)
buf[0] = value & 0xFF
# TODO properly handle multi byte reads
self._i2c_bus.writeto(address=self._i2c_adr, buffer=buf)
return
except OSError as e:
Expand Down Expand Up @@ -228,7 +229,7 @@ def __exit__(self, exc_type, exc_value, exc_tb):


def _validate_inputs(register: int, value: int, byte_count: int = 1, max_tries: int = 3):
if register < 0 or register > 255:
if register < 0 or register > pow(255, byte_count):
raise ValueError(f"Provided I²C device register {register} is out of range! (allowed range: 0 ≤ x ≤ 255)")
max_value = pow(256, byte_count) - 1
if value < 0 or value > max_value:
Expand Down
20 changes: 17 additions & 3 deletions feeph/i2c/emulation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -53,7 +53,10 @@ def readfrom_into(self, address, buffer, *, start=0, end=None, stop=True):
"""
i2c_device_address = address
i2c_device_register = -1
buffer[0] = self._state[i2c_device_address][i2c_device_register]
value = self._state[i2c_device_address][i2c_device_register]
for i in range(len(buffer)):
buffer[i] = value & 0xff
value = value >> 8

def writeto(self, address: int, buffer: bytearray, *, start=0, end=None):
"""
Expand All @@ -70,7 +73,15 @@ def writeto(self, address: int, buffer: bytearray, *, start=0, end=None):
i2c_device_register = buffer[0]
if i2c_device_register < 0:
raise ValueError("device register can't be negative")
value = buffer[1]
value = 0
# i must count up (0->len-1) to calculate the correct bitshift
# offset must count down (len->1) when populating the buffer
# 0x..## -> buf[2] -> i = 0, offset = 2
# 0x##.. -> buf[1] -> i = 1, offset = 1
# (buf[0] contains the register address)
for i in range(len(buffer) - 1):
offset = len(buffer) - 1 - i
value += buffer[offset] << i*8
self._state[i2c_device_address][i2c_device_register] = value

def writeto_then_readfrom(self, address: int, buffer_out: bytearray, buffer_in: bytearray, *, out_start=0, out_end=None, in_start=0, in_end=None, stop=False):
Expand All @@ -81,4 +92,7 @@ def writeto_then_readfrom(self, address: int, buffer_out: bytearray, buffer_in:
i2c_device_register = buffer_out[0]
if i2c_device_register < 0:
raise ValueError("device register can't be negative")
buffer_in[0] = self._state[i2c_device_address][i2c_device_register]
value = self._state[i2c_device_address][i2c_device_register]
for i in range(len(buffer_in)):
buffer_in[i] = value & 0xff
value = value >> 8
48 changes: 48 additions & 0 deletions tests/test_burst_handler.py
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,20 @@ def test_read_device_register(self):
# -----------------------------------------------------------------
self.assertEqual(computed, expected)

def test_read_device_register_multibyte(self):
state = {
0x4C: {
0x00: 0x1234,
},
}
i2c_bus = sut.EmulatedI2C(state=state)
# -----------------------------------------------------------------
with sut.BurstHandler(i2c_bus=i2c_bus, i2c_adr=0x4C) as bh:
computed = bh.read_register(0x00, byte_count=2)
expected = 0x1234
# -----------------------------------------------------------------
self.assertEqual(computed, expected)

def test_read_device_registers(self):
state = {
0x4C: {
Expand Down Expand Up @@ -75,6 +89,21 @@ def test_write_device_register(self):
# -----------------------------------------------------------------
self.assertEqual(computed, expected)

def test_write_device_register_multibyte(self):
state = {
0x4C: {
0x00: 0x0000,
},
}
i2c_bus = sut.EmulatedI2C(state=state)
# -----------------------------------------------------------------
with sut.BurstHandler(i2c_bus=i2c_bus, i2c_adr=0x4C) as bh:
bh.write_register(register=0x00, value=0x1234, byte_count=2)
computed = i2c_bus._state[0x4C]
expected = {0x00: 0x1234}
# -----------------------------------------------------------------
self.assertEqual(computed, expected)

def test_write_device_registers(self):
state = {
0x4C: {
Expand Down Expand Up @@ -146,6 +175,18 @@ def test_get_state(self):
# -----------------------------------------------------------------
self.assertEqual(computed, expected)

def test_get_state_multibyte(self):
state = {
0x70: {-1: 0x01},
}
i2c_bus = sut.EmulatedI2C(state=state)
# -----------------------------------------------------------------
with sut.BurstHandler(i2c_bus=i2c_bus, i2c_adr=0x70) as bh:
computed = bh.get_state(byte_count=2)
expected = 0x01 # byte count was ignored
# -----------------------------------------------------------------
self.assertEqual(computed, expected)

def test_set_state(self):
state = {
0x70: {-1: 0x00},
Expand All @@ -159,6 +200,13 @@ def test_set_state(self):
# -----------------------------------------------------------------
self.assertEqual(computed, expected)

def test_set_state_multibyte(self):
i2c_bus = sut.EmulatedI2C(state={0x70: {-1: 0x00}})
# -----------------------------------------------------------------
# -----------------------------------------------------------------
with sut.BurstHandler(i2c_bus=i2c_bus, i2c_adr=0x70) as bh:
self.assertRaises(ValueError, bh.set_state, value=0x0102)

# ---------------------------------------------------------------------

def test_no_timeout(self):
Expand Down