From 07b0bc6183f4dfea8e1443554e031a16c4b37c13 Mon Sep 17 00:00:00 2001
From: Jordan Speicher <jspeicher@xes-inc.com>
Date: Mon, 16 Jul 2018 17:31:29 -0500
Subject: [PATCH] Add raspberry pi EEPROM example

---
 examples/rpi_eeprom.py | 70 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 examples/rpi_eeprom.py

diff --git a/examples/rpi_eeprom.py b/examples/rpi_eeprom.py
new file mode 100644
index 0000000..5e2063e
--- /dev/null
+++ b/examples/rpi_eeprom.py
@@ -0,0 +1,70 @@
+"""
+Raspberry Pi EEPROM as defined in https://github.com/raspberrypi/hats/blob/master/eeprom-format.md
+"""
+
+import uuid
+import structures as st
+
+import crcmod
+
+
+class VendorInfoAtomData(st.Struct):
+    uuid = st.Bytes(16)
+    pid = st.Integer(2, byteorder='little')
+    pver = st.Integer(2, byteorder='little')
+    vslen = st.Integer(1)
+    pslen = st.Integer(1)
+    vstr = st.Contextual(st.String, lambda ctx: ctx['vslen'])
+    pstr = st.Contextual(st.String, lambda ctx: ctx['pslen'])
+
+
+class GPIOMapAtomData(st.Struct):
+    bank_drive = st.BitFields('hysteresis:2, slew:2, drive:4')
+    power = st.BitFields('_reserved:6, back_power:2')
+    pins = st.RepeatExactly(
+        st.BitFields('is_used:1, pulltype:2, _reserved: 2, func_sel:3'),
+        28
+    )
+
+
+class Atom(st.Struct):
+    type = st.Integer(2, byteorder='little')
+    count = st.Integer(2, byteorder='little')
+    dlen = st.Integer(4, byteorder='little')
+    #data = st.Contextual(st.Bytes, lambda ctx: ctx['dlen']-2)
+    data = st.Switch(
+		lambda ctx: ctx['type'],
+		cases={
+			1: VendorInfoAtomData(),
+			2: GPIOMapAtomData(),
+		}
+	)
+    crc = st.Bytes(2)
+
+
+class EEPROMData(st.Struct):
+    signature = st.Const(b'R-Pi')
+    version = st.Integer(1, byteorder='little')
+    _rsvd0 = st.Integer(1, byteorder='little')
+    numatoms = st.Integer(2, byteorder='little')
+    eeplen = st.Integer(4, byteorder='little')
+    atoms = st.Contextual(
+        lambda n: st.RepeatExactly(Atom(), n),
+        lambda ctx: ctx['numatoms'],
+    )
+
+
+
+atom_data = dict(uuid=uuid.uuid4().bytes, pid=0, pver=0, vslen=6, pslen=7, vstr=b'vendor', pstr=b'product')
+atom_data_built = VendorInfoAtomData().build(atom_data)
+atom = dict(type=1, count=0, dlen=len(atom_data_built)+2, data=atom_data, crc=b'00')
+atom_built = Atom().build(atom)
+crc_data = atom_built[:-2]
+crc = crcmod.predefined.mkCrcFun('crc-16')(crc_data)
+atom.update(dict(crc=crc.to_bytes(2, 'little')))
+
+eep = dict(version=1, _rsvd0=0, numatoms=1, eeplen=1, atoms=[atom])
+eep_built = EEPROMData().build(eep)
+eep.update(dict(eeplen=len(eep_built)))
+print(eep)
+