1 files changed, 80 insertions, 5 deletions

diff --git a/fpga/src/I2C.bs b/fpga/src/I2C.bs
index 2752acd..2a0614f 100644
--- a/fpga/src/I2C.bs
+++ b/fpga/src/I2C.bs
@@ -79,6 +79,22 @@ data I2CBusState
   | -- | We're reading SDA, which should be the ACK bit after sending an
     -- address.
     GetAddrAckReadSDA
+  | -- | TODO
+    WriteLowerSCL (Bit 1) (Bit 3)
+  | -- | TODO
+    WriteWriteSDA (Bit 3)
+  | -- | TODO
+    WriteRaiseSCL (Bit 1) (Bit 3) (Bit 1)
+  | -- | TODO
+    WriteAckLowerSCL (Bit 1)
+  | -- | TODO
+    WriteAckRaiseSDA
+  | -- | TODO
+    WriteAckRaiseSCL
+  | -- | TODO
+    WriteAckReadSDA
+  | -- | TODO
+    TODO
   | -- | We're about to either lower SCL or keep it low as part of reading a
     -- byte from a device.
     ReadLowerSCL (Bit 3) (Bit 1)
@@ -98,7 +114,13 @@ data I2CBusState
     -- hold, the second is the number of cycles to hold it for.
     ReadAckRaiseSCL (Bit 1) (Bit 1)
   | -- | TODO
-    TODO
+    StopLowerSCL
+  | -- | TODO
+    StopLowerSDA
+  | -- | TODO
+    StopRaiseSCL
+  | -- | TODO
+    StopRaiseSDA
   deriving (Bits, FShow)
 
 -- | Runs an I²C interface on the current clock.
@@ -164,8 +186,44 @@ mkI2C' rxSCL rxSDA txSCL txSDA addrReg dataReg statusReg = module
       state := if rxSDA == 1 -- NACK
                then TODO
                else if savedAddr[0:0] == 0 -- R/!W
-               then TODO -- !W
-               else ReadLowerSCL 7 1
+               then WriteLowerSCL 1 7 -- !W
+               else ReadLowerSCL 7 1 -- R
+      txSCL := 1
+      txSDA := 1
+    "WriteLowerSCL": when WriteLowerSCL bit n <- state ==> do
+      state := WriteWriteSDA n
+      txSCL := 0
+      txSDA := bit
+    "WriteWriteSDA": when WriteWriteSDA n <- state ==> do
+      let bit = savedData[n:n]
+      state := WriteRaiseSCL bit n 1
+      txSCL := 0
+      txSDA := bit
+    "WriteRaiseSCL": when WriteRaiseSCL bit n time <- state ==> do
+      state := if time == 1
+               then WriteRaiseSCL bit n (time - 1)
+               else if n == 0
+               then WriteAckLowerSCL bit
+               else WriteLowerSCL bit (n - 1)
+      txSCL := 1
+      txSDA := bit
+    "WriteAckLowerSCL": when WriteAckLowerSCL bit <- state ==> do
+      state := WriteAckRaiseSDA
+      txSCL := 0
+      txSDA := bit
+    "WriteAckRaiseSDA": when WriteAckRaiseSDA <- state ==> do
+      state := WriteAckRaiseSCL
+      txSCL := 0
+      txSDA := 1
+    "WriteAckRaiseSCL": when WriteAckRaiseSCL <- state ==> do
+      state := WriteAckReadSDA
+      txSCL := 1
+      txSDA := 1
+    "WriteAckReadSDA": when WriteAckReadSDA <- state ==> do
+      statusReg := statusReg { ready = True; dataAckBit = unpack rxSDA }
+      state := if rxSDA == 1 -- NACK
+               then StopLowerSCL
+               else TODO
       txSCL := 1
       txSDA := 1
     "ReadLowerSCL": when ReadLowerSCL n time <- state ==> do
@@ -201,9 +259,26 @@ mkI2C' rxSCL rxSDA txSCL txSDA addrReg dataReg statusReg = module
                then ReadAckRaiseSCL bit (time - 1)
                else if bit == 0
                then ReadLowerSCL 7 1 -- ACK
-               else TODO -- NACK
+               else StopLowerSCL -- NACK
       txSCL := 1
       txSDA := bit
+    "StopLowerSCL": when StopLowerSCL <- state ==> do
+      state := StopLowerSDA
+      txSCL := 0
+      txSDA := 1
+    "StopLowerSDA": when StopLowerSDA <- state ==> do
+      state := StopRaiseSCL
+      txSCL := 0
+      txSDA := 0
+    "StopRaiseSCL": when StopRaiseSCL <- state ==> do
+      state := StopRaiseSDA
+      txSCL := 1
+      txSDA := 0
+    "StopRaiseSDA": when StopRaiseSDA <- state ==> do
+      state := Idle
+      statusReg := statusReg { busIdle = True }
+      txSCL := 1
+      txSDA := 1
   return ()
 
 -- | Returns an I²C interface that runs on the current clock. This is not what
@@ -216,7 +291,7 @@ mkI2C rxSCL rxSDA = module
   dataReg <- mkReg 0
   statusReg <- mkReg (I2CStatus
     { ready = True
-    ; busIdle = False
+    ; busIdle = True
     ; addrAckBit = False
     ; dataAckBit = False
     ; arbitrationLost = False