From 82c90d70279c9522520f864daa72156fdacf38b1 Mon Sep 17 00:00:00 2001
From: Christian Pointner <equinox@spreadspace.org>
Date: Sun, 7 Jul 2013 02:46:24 +0000
Subject: bootloader now checks csum

git-svn-id: https://svn.spreadspace.org/pic/trunk@47 a09c6847-51d9-44de-8ef2-e725cf50f3c7
---
 bootloader/bootloader.asm | 44 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 10 deletions(-)

(limited to 'bootloader/bootloader.asm')

diff --git a/bootloader/bootloader.asm b/bootloader/bootloader.asm
index ff23d61..6df5906 100644
--- a/bootloader/bootloader.asm
+++ b/bootloader/bootloader.asm
@@ -66,6 +66,7 @@ CMD_R_CONFIG    EQU       .8
 CMD_W_CONFIG    EQU       .9
 
 CMD_MAX         EQU       .9
+CMD_MIN_LEN     EQU       .3
 
   ;; Variables
 combuff         EQU       H'0020'
@@ -75,7 +76,7 @@ current_cmdlen  EQU       H'0070'
 csum            EQU       H'0071'
 
 flags           EQU       H'007D'
-#define F_NEW_CMD         flags,0
+#define F_CMD_STARTED     flags,0
 
 cnt2            EQU       H'007E'
 cnt1            EQU       H'007F'
@@ -186,7 +187,7 @@ uart_rx_byte              ; process received command
   movf      RCREG,w
   movwf     INDF
   incf      FSR,f
-  btfss     F_NEW_CMD
+  btfss     F_CMD_STARTED
   goto      wait_cmd_len
   movf      current_cmdlen,f
   btfsc     STATUS,Z
@@ -200,7 +201,7 @@ uart_rx_fe                ; recover from framing error
   goto      wait_new_cmd
 
 wait_cmd_len
-  bsf       F_NEW_CMD
+  bsf       F_CMD_STARTED
   goto      wait_cmd
 
 new_cmd                   ; got new command code
@@ -208,13 +209,15 @@ new_cmd                   ; got new command code
   sublw     CMD_MAX
   btfss     STATUS,C
   goto      invalid_cmd
-  decfsz    combuff + .1,w
-  goto      load_cmdlen
+  movlw     CMD_MIN_LEN         ; check for minimum command len
+  subwf     combuff + .1,w
+  btfss     STATUS,C
   goto      invalid_cmd
-load_cmdlen
+  movlw     .2                  ; 2 bytes already received
+  subwf     combuff + .1,w
   movwf     current_cmdlen
-  decfsz    current_cmdlen,f
   goto      wait_cmd
+
 invalid_cmd               ; received command code is not known or len is bogus
   movlw     E_INV_CMD
   movwf     combuff + .2
@@ -222,9 +225,23 @@ invalid_cmd               ; received command code is not known or len is bogus
   call      send_answer
   goto      wait_new_cmd
 
-exec_cmd                  ; command is correct and complete
-  ;; TODO: check csum
-  movf      combuff,w     ; dispatch commands
+exec_cmd                        ; command is complete -> check csum
+  movlw     combuff
+  movwf     FSR
+  movf      combuff + .1,w
+  movwf     cnt1
+  clrf      csum
+exec_cmd_check_csum
+  movf      INDF,w
+  xorwf     csum,f
+  incf      FSR,f
+  decfsz    cnt1,f
+  goto      exec_cmd_check_csum
+  movf      csum,f
+  btfss     STATUS,Z
+  goto      csum_error
+
+  movf      combuff,w           ; command is correct and complete -> dispatch
   addwf     PCL,f
   goto      wait_new_cmd
   goto      cmd_identify        ; identify
@@ -237,6 +254,13 @@ exec_cmd                  ; command is correct and complete
   goto      cmd_not_impl        ; read config
   goto      cmd_not_impl        ; write config
 
+csum_error                 ; received command has an invalid check sum
+  movlw     E_BAD_CSUM
+  movwf     combuff + .2
+  movlw     .1
+  call      send_answer
+  goto      wait_new_cmd
+
   ;; ** Command Handlers ********************
   ;; ** identify *******
 cmd_identify
-- 
cgit v1.2.3